I do think that he is indeed at the wrong here. But as a college student, I'm trying to think of why he might have such beliefs and these are my thoughts

He could have had an experience in the past, could be in high school but most likely in college, especially with women, that caused him to think in such a way.

I know that college kids are treated as adults but our mind is still at a developing stage and we (college students) are still forming our personality (at least imho). I think something may have happened that he hasn't told you about that may have influenced his personal beliefs and affected his personality. (Maybe a girl he was with cheated on him, I'm not too sure)

At the risk of sounding ignorant and judgmental, in modern society, more people are sexually active and upfront. And most of college girls in my own experience, wear more revealing clothes and don't exactly dress or act conservatively. (You wouldn't believe what some people define shorts/pants nowadays) Again don't mean to offend anyone but trying to see why he may think in such a way.

At the end of the day, I think you and your husband should talk to him and try to understand why he may hold on to these beliefs first. I know that you guys are upset and maybe even angry. Sure, he may refuse to reason with you and even refuse to talk to you regarding the matter. He may also refuse to change his beliefs. But before making decisions you may come to regret, I think it's a good idea to try and see things from his perspective.

I really hope your fanily can work this out and become even closer together. After all, we hunans bond better with each other after facing hardships together.

I wish you and your family the best!