Hi, there. I'm happy to help with this.

Some religious traditions have opposed the representation of the human form in religious art. In particular, the representation of divine personage with human characteristics is seen as demeaning to those who do not share the gender, racial, ethnic, age or other human characteristics portrayed in the representations of divine personages.
Which of the following, if true, would constitute the strongest challenge to the validity of these concerns?

So, the claim is: the representation of sacred in a specific human form (most often male, and many times white) can be seen as demeaning to folks of different gender, race, ethnicity, etc. etc.

A: Religious traditions are emotional and not logical
This is tantamount to saying: we can't use any logic when discussing an argument that touches on the topic of religion. That's never an approach the GMAT CR will take --- the GMAT will only present arguments that admit of logical analysis.
Furthermore, this argument is not about theological ideas. Rather, it is essentially a sociological statement --- some folks are going to take offense at certain images. Sociology is a legitimate academic discipline that certainly admits of logical analysis, so this answer is off the mark. A is out.

B: Religious art without the human form is meaningless
First of all, this is a awfully hard to justify statement. It seems quite extreme to say that the Alhambra, the Yin/Yang, the OM symbol, Tibetan Buddhist mandalas, and totem poles of the Pacific NW Native Americans are all "meaningless" because they don't contain the human form!! Extremism is never correct on the GMAT.
Furthermore, if people are offended by the sacred in human form, then they are offended. Telling them that the religious art wouldn't work without the human form is not going to make them any less offended. This is not only extremist but completely irrelevant. B is out.

C: Research has failed to find anyone who shows evidence of being demeaned by representation of divine personages
The argument is concerned that human representations of the sacred will offend, or could offend, some people. That's essentially a sociological claim. If sociological study has failed to find anyone who actually is offended, that's a pretty big challenge to the claim. C is a strong candidate for the answer.

D: Most religions do not oppose the representation of the human form
That may be true, but it's irrelevant. People are offended, and whether the religion says the image is OK is not likely to make a difference to the folks offended. Suppose a Christian church has a painting of the Christian Lord as a white northern European, and some non-white folks take offense at this depiction and lodge a complaint. If the church tells them: well, the image is permitted by our church policy, that is not likely to assuage the offense of those who complained --- if anything, it's likely to incense them further! Again, the offense people are taking is more a sociological fact, and religious justifications are not going to make it go away. [spoiler]D may be true but it's irrelevant[/spoiler].

E: All people are equal in eyes of God
First of all, this is a theological statement, which really has no place in a GMAT CR argument. I agree this is a lovely sentiment, but it's not the kind of statement for which one can provide social science evidence, so it's not a valid point in the context of GMAT CR.
And again, the offense people take at certain images is a sociological fact. If we tell the folks who are offended, "But, all people are equal in the eyes of God", then they may well say, "Well, if that's true, then why do you represent God as an old white man instead of as a woman or a person of color?" In other word, telling them this theological truth will not make their offense vanish -- in fact, they may well believe something like this theological view already and that's part of the reason they are offended in the first place. [spoiler](E) in no way challenges the arguments[/spoiler].

So we have four answers that don't work at all, so the only valid answer is C.

Here's a very different CR question, for further practice:
https://gmat.magoosh.com/questions/1280
When you submit your answer to that, the next page will have the complete video explanation.

Does all this make sense? Let me know if you have any further questions.

Mike