well, another poster mentioned an elder that used to constantly harp about fornication who ended up being guilty of that himself.
I had an elder in Bethel tell me off for having a classical CD with a very romantic picture of a man and woman kissing on it. He was shortly after disfellowshipped for having a 7 year affair. One of my room mates in Bethel used to regularly berate gays, yet later told me he had been in a homosexual relationship a couple of years prior to coming to Bethel. People can make a big deal over things they have a personal struggle with.
Another reason they fear homosexuality, is that it is a great threat to numbers. Homosexuality cannot be "cured", as much as they argue otherwise, and they know that if a person is disfellowshipped for homosexuality it is very unlikely they will return.