I'm interested in your distinction "sufficiently opposed to gays marrying to spend money on it". This has turned up quite a few times in these threads. Apparently merely being opposed to gays marrying is, like, unfortunate, but doing anything about it crosses the line to absolutely insufferable. Are you saying this? Then what's the point of being "allowed" to have an opinion some people don't like, if actually doing anything about it is "wrong"? Is it the money that makes it bad? Trying to convince others to your viewpoint? Any action besides just voting? Is voting against gays marrying worse than just thinking to yourself that they shouldn't?
This may again be nitpicking, but I'm not trying to argue, just wondering where people draw the lines.
Thus, while it is fine to prefer gays not marry, it is wrong for group a to exert power against group b to limit group b's freedom when group a suffers no harm either way.
Having the opinion is questionable. But when you exert your power over another group, you enter a sphere of active rather than passive bigotry.
You only donate to anti prop 8 if you are sufficiently opposed to gays marrying to spend money on it. I think it is by definition a bigoted act, and to use your words, morally repugnant.