I am not really sure; I just reread an answer I posted a few months ago, and can't understand a word I was saying!
I would suggest that one of the reasons sexuality is so contraversial is because it is our prime motivator in life (drives ambition - going back to the freudian outlook, which I believe is very true).
Add to that the fact that until 50 years ago, sex was hush hush; the sixties saw a 'revolution' which forced sex out in the face of the public, homosexuality became a matter of debate (before then it had just been regarded as a criminal offence). I guess that particular period in our history brought sex to the fore, and therefore something new for people to cope with. I actually remember the Kinsey report being talked about - mostly in a humourus way (because people were trying to sound as if they were quite happy discussing sex - when they probably weren't.)
Since then, we have had the 'innovations' of all forms of sexuality being explored, the exploitation of pornography, contraception being openly discussed; the advances in medicine (in all aspects of sexuality); thinking about it, it is no surprize that sexuality is contraversial. The whole subject has been raked up from under the carpet, and put out for everyone to look at and discuss; the Church got in on the act.....
I guess we have come a long way in the last 50/60 years; change can't be quick without breaking a few eggs.