I've long believed railing out against homosexuality is one of the causes for declining church membership. A survey found the states where churches successfully lobbied their state legislatures to outlaw gay marriage were the states that experienced the largest church decline.
To envision how stupid it is for churches to condemn homosexuality, we first need to look at its "cause." There is no "cause." We don't know why some people are attracted to the same sex. We only know it is not their choice. Calling people with blue eyes "sinners" it would be just as ridiculous as calling gay people sinners.
Second, think of the numbers. No one knows for sure the percentage of the gay population but mostly it is considered five to ten percent. Let's use the number five percent. In a church youth group of just 20 kids, there will be a gay kid. That kid will have friends. Plus, he/she will have brothers, sisters, parents, grandparents, other relatives and their friends. Is it smart to offend all these church people for no reason at all?
If a preacher feels it necessary to talk about "sin" it's much better to condemn something not in the community. "Hollywood" is a good one. Or maybe "San Francisco" will work. Or, maybe it's safest to just condemn"sin" generically without naming a sin or a place.
Homosexuality has been here since there have been humans. It will be here long after Christianity.