They don't.
They worry about it when homosexuals want special rights.
They worry about it when homosexuals want homosexual marriage legally recognized.
They worry about it when homosexuals want it taught that it's an acceptable lifestyle alternative to kindergarteners.
They worry about it when what's supposed to be a private act between two consenting adults in the privacy of their own bedroom is lauded and trumpeted in the streets and shoved in our faces daily.
They're hypocrites. If it's done in the privacy of their own bedrooms and nobody else's business, then why do they keep making it everybody else's business? Keep it there like they say it should be and stop rubbing our noses in it and demanding that it be accepted as normal. It's not. It's not morally and it's not biologically.
Well stated -Bravo!