I don't support gay marriage. Civil union yes. Marriage no.
I think gay couples shouldn't be allowed to adopt children either.
I think gay campaign groups have to much money and influence on politics today.
Am I homophobic?
I think that these kinds of questions can be answered by taking the original question and applying it to other groups. Is not supporting women's sufferage and believing women should be housewives sexist? Is believing that interracial marrage should be illegal and that segregation is a good policy racist? If you can look at your question from another angle you will often find what you were originally looking for.