I'm going to be blunt with you. All sex outside of a marriage is a sin according to the Christian Church. This includes both homosexual and heterosexual activity. I know I am delving into a sensitive and controversial topic, but I don't care. Yes, I am going there.
Discriminating is hurtful. I say if individuals want to discriminate against gay activity then they too should single out premarital sex offenders which would be a lot of us. Generally so to speak, we are all sinners whether homosexual or heterosexual. It's important to love the sinner, and hate the sin.
Homosexuals deserve respect and human treatment. The only place that should be allowed to turn them away is at the Church for gay marriage services.
The church is protected by the First Amendment which guarantees freedom of religion, speech, assembly, and petition. It states that Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof. The church has the right to exercise its beliefs that homosexuality is not recognized as a matrimonial union in the eyes of God. It is a sin to God. Below is Matthew 1:26-27.
The individuals who committed homosexuality were punished and it was viewed as a sinful error during Biblical times. It is still viewed that way in many churches.
Churches should not have to violate their own Biblical beliefs to marry gay individuals. There are other churches that will marry them. Homosexuals can marry in those churches and not push the churches who have a doctrine that strictly tells them not to do so. Turning away gay couples should be done in a respectful manner. Again, the Bible calls us to love one another or love the sinner, hate the sin.