Gult by association is an attempt to discredit an argument or idea by associating it with something the audience would not approve of.
This is a fallacy of inductive reasoning, which means it argues from particular examples to the universal. This is the opposite of syllogistic arguments, which are deductive,, moving from universals to particulars: for example, All men are mortal, therefore Socrates is mortal. A typical inductive argument might look something like this:
Premise. I have seen hundreds of swans, and they were all white.
Conclusion. Therefore, all swans are white.
In a deductive argument, the conclusion necessarily follows from the premises: if they are true and the argument is valid, then the conclusion must be true. Obviously, this isn't the case with an inductive argument: it's possible for the conclusion to be false even if the premises are true. (All it takes is to find a black swan: they do exist.) Inductive reasoning relies on probability: the stronger the premises, the greater the likelihood that the conclusion is true.
More specifically, guilt by association is a form of hasty generalization, in which the sample size isn't large enough to support the conclusion. Just because a certain position or thing and something unpleasant share one characteristic, doesn't mean they share enough characteristics to be actually connected.
Guilt by association is very similar to the formal fallacy of the undistributed middle term.
This is one of those fallacies that's simple enough to concoct, simply by invoking Nazis:
Why would I want to be a vegetarian? Hitler was a vegetarian, you know.
The wrongheadedness of this argument is easily exposed simply by pointing out many of the other innocent things Hitler did: breathe, love his mother, drive in cars, and so forth. You wouldn't want to be like Hitler, would you?
NKJV changes "end of the WORLD" to "end of the AGE"! And in it's [sic] no longer the "WORLD to come" but "AGE to come". The New Age Movement teaches a series of ages (hence the name: New AGE). See Matthew 12:32, 13:39, 13:40, 13:49, 24:3, 28:20, Mark 10:30, Luke 13:30, 20:34,35, 1 Cor 1:21.
The New Age Movement and the occult are longing for one called the Maitreya. The Bible calls him the Anti-Christ. New Ager's [sic] refer to him as the "the Coming One" - AND SO DOES THE NKJV! In Luke 7:19, 20 (see also Matt 11:3) John told his disciples to ask Jesus: "Are You THE COMING ONE. . ." In the [sic] "The Great Invocation", a "prayer" highly reverenced among New Agers and chanted to "invoke" the Maitreya, says, "Let Light and Love and Power and Death, Fulfil the purpose of the Coming One."
And to REALLY show their sympathy with the satanic New Age Movement - BELIEVE IT OR NOT - in Acts 17:29 the New Age NKJV changes "Godhead" to "Divine Nature"! (ditto NIV, NASV [sic]) (all emphases in original)
Watkins apparently expects us to believe NKJV is a "New Age" Bible simply because of a superficial similarity in wording: New Age sources also use a few of the same, fairly common, words. If I rewrite Watkins' argument syllogistically, the undistributed middle becomes obvious:
Premise 1. The NKJV uses the term "the Coming One" [or "age" or "Divine Nature"].
Premise 2. New Agers use the term "the Coming One."
Conclusion. Therefore, the NKJV is New Age.
True or not, the conclusion simply doesn't follow.
Watkins apparently is unable or unwilling to entertain alternatives as to why the NKJV reads as it does: for example, that "age" is a proper translation of the Greek term aion, which refers to an age of time, and from which we get our English word eon (and arguably a better rendition than the KJV's "world"); "the coming one" is a proper (and literal) translation of erchomai (and is it really any less accurate than the KJV's "he that should come"?), and "Divine Nature" is a valid rendering of theios. Indeed, the last is in fact synonymous with "Godhead": the suffix -head is an archaic form of -hood, which denotes state or quality. In other words, "Godhead" means "the state of being God" - in other words, divine nature. It's also fair to point out that 2 Pet. 1:4, uses those very words. Is it also a New Age Bible?
My first experience with Dial-the-Truth and Watkins was their page titled "Christian Rock: Blessing or Blasphemy?" in which (amongst other things) Watkins criticized DC Talk - primarily by avoiding discussing DC Talk, and talking primarily about Nine Inch Nails. Why? Because the director of NIN's "Closer" video, Simon Maxwell, also directed DC Talk's video for "Jesus Freak." I'm inclined to think that if guilt by association didn't exist, Watkins would have nothing to say.
As with the fallacy of the undistributed middle term, the proper rebuttal to guilt by association is to point out that surface similarities do not a connection make. Point out any relevant dissimilarities that weaken the case. And, if possible, expose the argument's absurdity.