Discrimination is not automatically bad. I discriminate on the kinds of foods I eat, on the programs I watch, and what movies I let my kids see. In fact, we all discriminate. We all have criteria by which we judge what is and is not acceptable. I discriminate against child molesters, and I will not let them be with my children unattended. I discriminate against various theological teachings that contradict the Bible. I discriminate all the time and so do you.
When it comes to homosexuality, I believe that God has condemned it as a sin (Rom. 1:18ff). But my agreeing with God that homosexuality is a sin is not the same as discriminating against homosexuals. I have no problem working with homosexuals in a secular environment. I have no problem with homosexuals being my neighbors. I have no problem with working out at the gym with homosexuals. In things like these, I don't discriminate.
Likewise, I would agree that someone should not be fired from a job (in the secular realm) because he or she is homosexual. I think that is wrong not because it is based on sexual orientation but because we should treat everyone as equally as possible.
Furthermore, because of my religious beliefs and my right to express them, I would not promote homosexuality, nor would I change my preaching and teaching so as not to "offend" those who think that having sex with people of the same gender is perfectly normal and morally acceptable. The fact of the matter is I'm offended by their lack of moral sensibilities. But no one seems to be concerned about how I'm offended or how I feel about the intrusion of homosexuality into society, TV, the movies, etc. But, I digress.
To say that condemning homosexuality is wrong is a statement dealing with morality--not with legality. There might be various laws for and/or against homosexuality, but saying that condemning homosexuality is wrong is a moral issue. My question then would be by whose standard is something right or wrong, and what justifies that standard as being valid? Yes, I know, a homosexual can ask me the same question; and we could debate it, but that is another conversation.
If an atheist were to say that condemning homosexuality as a sin is morally wrong, then on what basis does such a statement gain its moral objectivity by which a blanket condemnation can be made? If someone says that the majority of society determines what is morally right and wrong, that is called the fallacy of Argumentum ad populum. Just because a majority of people think something is right or wrong doesn't make it right or wrong.
So, when a person objects on moral grounds to my objections or other Christians condemning homosexuality as a sin, he has no objective moral basis by which he can make such an assertion. At best, all he is doing is giving his opinion; and it would be arrogant to think that his opinion is the standard of morality for everyone else.
Condemning homosexual practice as a sin is not discriminatory in a legal sense; but it is one in a spiritual sense, and that is alright.