It's not OK to have a preference for something you can't actually see or feel the difference.

Oh people can tell the difference. I've seen plenty through various sources and they do not look like real vaginas. They really need to stop fooling themselves.

Even if you couldn' t tell the difference, knowing there is a difference is plenty ok to reject someone.

I can' t tell just by looking if someone is a religious extremist or not, but if I am told, you can bet your ass I am going to take it into consideration when deciding whether to date him or not. Same goes with everything. It doesn' t matter how stupid it is, if it makes you think "I am not so sure about fucking/dating this person", then it' s ok.