There are plenty of gay people who opposed gay marriage - go out, find them and ask them.
I don't need to - I'm already aware of them. What matters is whether somebody is against something for themselves but is happy for others to avail themselves of it if they want to (which is typically the attitude I saw in gay people who opposed equal marriage - they were uninterested rather than actively hostile, regarding it as superfluous) or whether somebody thinks their opposition to something is such that they're entitled to try to forbid it others. Many opponents of equal marriage fell into the latter category.
Not sure that there are any longitudinal studies to prove or disprove this assertion, Shakes.
You could always have a look.
So, since you believe that their opinion to be bizarre, it clearly shows that you are prone to "odd, obnoxious, pernicious and discriminatory beliefs".
No, as I'm not seeking to discriminate against those who hold such beliefs, as were some of those on the opposing side who opposed the introduction of equal marriage. Merely finding something bizarre is not discriminatory. Nor are my beliefs odd, given that there was clear majority support for equal marriage before it was introduced. In such a situation the minority opinion would be the odd one, wouldn't it.