Although none of the few mentions of homosexuality in the Bible are references to stable, monogamous, life long gay relationships.
Given that in Matthew 7:12 Jesus sums up the whole of the Law and the Prophets as "do to others what you would have them do to you", if you would like to marry someone of the same gender, and they would like to marry you, then there is no transgression of the Law.
I would say that the theological case against gay relationships is not as open-and-shut as many Christians say. It is a complex issue which can't be resolved by citing a few verses (and there are only a few) out of context. There is no single method of biblical interpretation agreed on by all Christians, there never has been, so differences of opinion and conscience have to be catered for. Even if the Bible were straightforward on this issue (which it isn't), it raises the question whether Christians have to base their personal theology on scripture alone (which none of us do in practice, even the minority who claim they do), or whether tradition, reason, experience, etc. also bear on our decisions, and if so how they should interact in our theological deliberations.
There are many other issues which were as controversial in their day as gay marriage is for the church at present, but we have managed to get over them. Take lending at interest, for example. It is criticised in the Old Testament, criticised in the New Testament, the Early Church Fathers were against it and it was preached against by the church for the first thousand years of its existence. But today nobody bothers about it. If someone in your church wants you to write to your MP about gay marriage, first insist that they write to their MP about personal loans being offered by High Street banks. If they refuse point out that they are being unbiblical and contradicting church tradition. If they still look at you askance, ask them whether they are really concerned about what the Bible says.
And I say all of this as a deeply committed churchgoing Christian, who also happens to believe in equality for gay people.
I left the Catholic faith some time ago, but even before that I would have had trouble discriminating against others, as you're feeling now. After all, Jesus taught tolerance of others and treat others as you would wish to be treated yourself.
I attend a rc church and we are being urged to voice our objection to the marriage bill. I am having trouble with this as it seems to discriminate against same sex relationships. I know there is evidence in the bible indicating that same sex relationships are not part of god's plan. However, i also belive in understanding and not victimizing sectors of society. How do others feel? Thank you