I have not read anything of Charles Murray (that I am aware of), I just pulled that from Wikipedia, and in that it notes that it was one chapter of the Bell Curve, not the entire thesis, so you are correct. I honestly don’t feel comfortable speaking about him at all because my entire universe of knowledge is this article and a quick trip to his wikipedia page.
Because we seem to be having trouble on agreeing as to who is a fringe person worthy of being labeled fringe and who isn’t, I think the best way to discuss the protest angle is to go to the extreme. Let’s say David Duke is invited to speak at a college campus by a small club at the school. Do you think it would enhance or encourage critical thinking to force allow such a vile man have a platform on the campus? Wouldn’t the mere fact that the speaker was approved signal to a portion of the student body that hate speech and ethnic-tribalism is okay? Is that even worthy of debate?
Conversely, in the David Duke hypothetical, wouldn’t blocking his ability to use the college campus through peaceful protest said a powerful message to David Duke, that group that invited him, and the school itself that those racist and evil beliefs are not acceptable?