While "homosexual" acts are sinful and cannot be condoned, so are hatred and discrimination. The argument I make about same sex attractions being disordered must not be used to discriminate against people with these attractions. The only Christian response to persons with same sex attractions is love and compassion.
No person that claims to be a Christian can discriminate against anyone who has same sex attractions. This, however, does not mean that a Christian should allow legislation to pass that would allow what is call "same sex marriages." Stopping same sex couples from joining in what they call a "marriage" is not discrimination, but is the only responsible thing to do for these couples and for society.
So-called "homosexual" acts are harmful to the persons engaging in them and to society as a whole. By allowing legislation to pass that would attempt to legitimise such acts, one would be in part responsible for the sin committed by the persons that then participate in these so-called "marriages." Any action that would condone "homosexual" acts, even if law requires such action, is a sin against those committing these "homosexual" acts, and against society.
I am thinking of the 2005 case in Port Coquitlam, British Columbia where the local Knights of Columbus council declined to rent their hall to a couple for a lesbian "wedding" reception. This was not discrimination, but the only just thing for this council to do for the lesbian couple and for society. If they had not declined, they would have be in part responsible for the immoral union celebrated at this reception, and fully responsible for the message it would speak to their community; a message directly opposed to the teachings of the Catholic Church.
This Knights of Columbus council did not discriminate against this lesbian couple, but let this couple know that what they were celebrating was not a wedding and not morally acceptable. The British Columbia Human Rights Tribunal, however, did discriminate against this Knights of Columbus council by forcing them to pay the lesbian couple each $1000 plus legal costs. These Knights of Columbus were penalised by the British Columbia government for being responsible Catholics.
Discrimination against persons with same sex attractions is wrong, but not speaking up about the immorality of so-called "same sex marriages" is just as wrong.