Dan 11:33 And they that understand among the people shall instruct many: yet they shall fall by the sword, and by flame, by captivity, and by spoil, many days.

Dan 12:3 And they that be wise shall shine [teach, shed light] as the brightness of the firmament; and they that turn many to righteousness as the stars for ever and ever.
Dan 12:4 But thou, O Daniel, shut up the words, and seal the book, even to the time of the end: many shall run to and fro, and knowledge shall be increased.

The Bible clearly says that "knowledge shall be increased".  This should be sufficient to utterly refute and embarrass into silence those people who refuse to believe current sound doctrine on the sole basis that it was not taught by the early Church Fathers, or not until the last 100 years.

Not only does the Bible teach this basic principle that knowledge shall increase, but it is especially true since the advent of the internet.  

Now, it is very ironic that many people who scorn Bible commentaries (or who scorn any modern knowledge) are not afraid to write their own commentaries.  That is the ultimate in hypocracy, and if their twisted logic was sound, then they would have no basis for writing anything of their own.

Another group of people scorn commentaries because they want to believe the "Bible only," and they want to reject anything written by man.  But unless you are a Greek Scholar, who has studied Ancient Greek (not modern Greek), then your knowledge of what the Bible says is contaminated by the biases of the men who created the translation you are reading.  And even if you studied to know Ancient Greek, you are still at the mercy of the men who write the dictionaries of Ancient Greek!  Therefore, it is impossible to try to reject the contribution of knowledge of all men, thinking to adhere to the "Bible only".  These scorners hypocritically cry for "sola scriptura", or "Bible only", and that we should "reject ALL the doctrines/commandments of men", as they misquote the following verses:

Titus 1:14 Not giving heed to Jewish fables, and commandments of men, that turn from the truth.

Ephesians 4:14 That we henceforth be no more children, tossed to and fro, and carried about with every wind of doctrine, by the sleight of men, and cunning craftiness, whereby they lie in wait to deceive;

1John 2:27  '...ye need not that any man teach you..."

But these verses do not prove that everything taught by a man is bad.  The Bible gives high praise to those who teach, and God has said that he will provide teachers to the Church.  If you believe the Bible at all, you must acknowledge that God will provide men who will stand up for and teach sound doctrine to the Church.

1Timothy 5:17 Let the elders that rule well be counted worthy of double honour, especially they who labour in the word and doctrine.

1Timothy 4:13 Till I come, give attendance to reading, to exhortation, to doctrine.

Titus 1:9 [A biship must be...] Holding fast the faithful word as he hath been taught, that he may be able by sound doctrine both to exhort and to convince the gainsayers.

Titus 2:1 But speak thou the things which become sound doctrine:

Eph 4:11 And he [God] gave some, apostles; and some, prophets; and some, evangelists; and some, pastors and teachers;
Eph 4:12 For the perfecting of the saints, for the work of the ministry, for the edifying of the body of Christ:
Eph 4:13 Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ:

Just because there are warnings about "bad doctrine", that does not mean that all doctrine taught by men is bad.  But fools reject wisdom, and cannot learn, and "none of the wicked shall understand."

Proverbs 23:9  Speak not in the ears of a fool: for he will despise the wisdom of thy words.

Dan 12:10 Many shall be purified, and made white, and tried; but the wicked shall do wickedly: and none of the wicked shall understand; but the wise shall understand.

The wicked are in a spiritual darkness that prevents them from learning.  They are lazy in the mind and spirit, refusing to think deeply about scripture, choosing instead to be willfully ignorant, and/or they open themselves up to "doctrines of devils".

1Ti 4:1 Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils;

Now, a good commentary can turn the tide of popular opinion regarding the interpretation of scripture, and this is God's intent, as we saw in Ephesians 4:12-13, as the purpose of teachers, among others, is to help bring in unity of the faith.  

But some people don't understand why there must be arguing and disputes about doctrine, thinking that such things "cause division", which is in contrast to the unity that God intended there to be in the Churches. 

However, the fools and false teachers will always be with us; and thus, they will always need to be refuted.

1 Corinthians 11:19  For there must be also heresies among you, that they which are approved may be made manifest among you.

Therefore, the purpose of debates about what scripture says, and the purpose of all commentaries, even the bad ones, are to help you to see which interpretation is a heresy (in error), and which interpretation is "approved".  I believe that even reading commentaries that teach false doctrine is beneficial, because doing so helps one to exercise discernment, which you, the reader, will need to prevent from being deceived, which gives us the ability to "try the spirits".

Hebrews 5:14  But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.

1 John 4:1  Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world.

So, in writing commentaries, I am following the Bible's commands to rebuke false doctrine, and to provide reasons for why I believe what I do:

2 Timothy 4:2  Preach the word; be instant in season, out of season; reprove, rebuke, exhort with all long suffering and doctrine.

Titus 1:13  This witness is true. Wherefore rebuke them sharply, that they may be sound in the faith;

1 Pet 3:15  But sanctify the Lord God in your hearts: and be ready always to give an answer to every man that asketh you a reason of the hope that is in you with meekness and fear:

Those of you who read commentaries are following Bible commands:

to "exercise discernment" (Heb 5:14),
to "try the spirits" (1 John 4:1),
to "give attendance to reading, to exhortation, to doctrine" (1 Timothy 4:13), to "meditate" and carefully think about the Word of God (1 Timothy 4:15),
to "study to show thyself approved unto God" (2 Timothy 2:15),
to demonstrate your honour as you "search out a matter" (Prov 25:2),
to show your nobility as you "search the scriptures daily" (Acts 17:11), and
to "grow in grace, and in the knowledge of our Lord and Saviour Jesus Christ" (2 Peter 3:18).

Prophecy teaches us greatly about the sovereignty and nature of God.  God can speak or write something quite clearly, yet he can also keep something hidden from mankind, to keep man from understanding it until the proper time.  God works like this to show his sovereign nature, that God is in complete control, and that truth comes directly from the Father.  Here are two important examples of how God reveals things only at the proper time, even though he has prophesied, and spoken clearly, beforehand.

First, when Jesus told his disciples that he was going to die, they did not understand it. 

Luk 9:44 Let these sayings sink down into your ears: for the Son of man shall be delivered into the hands of men.
Luke 9:45 But they understood not this saying, and it was hid from them, that they perceived it not: and they feared to ask him of that saying.

Luk 18:32 For he shall be delivered unto the Gentiles, and shall be mocked, and spitefully entreated, and spitted on:
Luk 18:33 And they shall scourge him, and put him to death: and the third day he shall rise again.
Luke 18:34 And they understood none of these things: and this saying was hid from them, neither knew they the things which were spoken.

Thus, Jesus spoke plainly, but the disciples STILL did not understand, and neither did God's enemies.

1Co 2:7 But we speak the wisdom of God in a mystery, even the hidden wisdom, which God ordained before the world unto our glory:
1Co 2:8 Which none of the princes of this world knew: for had they known it, they would not have crucified the Lord of glory.