First off we as Christians should stop making homosexuals the main target of our anti-sin crusade. In fact we need to stop any anti-sin crusade.
Witness with your every day actions and speak the truth in individual situations. Be Christlike to a sick world! Chime in your opinion at appropriate times with class and kindness. That being said, do not hold back on dishing out truth.. for we are NOT ashamed of the Gospel of Christ! But pick your battles wisely.
Why is homosexuality so bad?
It's very simple. It is the ultimate in sexual rebellion against God.
The classic response is, why should one's preference bother someone if it doesn't harm anyone?
Does your gayness harm me as an individual? Absolutely not. Not directly.
But sin has an almost karma like affect on all of us.. even personal sin. The deterioration of the nuclear family is a major problem in my opinion.
A related side note...
I have been interested in the psychology and sociology of serial killers from as far back as the 19th century. You will nearly always find deviant or overbearing parents involved in the raising of a serial killer. And so very often homosexuality is involved. Ed Gein, John Gacy, Dennis Nilsen, Jeffrey Dahmer, and Ottis Toole are a few that come to mind. There are many more in fact the number of serial killers who are homosexual is generally thought to be well above 60%.
The above stat is not to say that every homosexual has serial killer tendencies but it is fascinating that the reverse may be true.
I as a Christian am not going to start an anti-gay campaign. God gave us free will. But I will not water down the fact that it is a sin. It's a sin. And let's face it... it's just gross.