No you're redefining "false logic".
If we were to be pure to your theoretical frictionless-vacuum definition of equality then you would also need to be vehemently opposed to our treatment of child molesters, thieves and liars. We have plenty of targets of hate in our culture. The gay marriage debate though is tricky because a lot of people still think denying rights to gays is a 'justifiable' hate. Liberals however find it an unjustifiable hate.
It's tricky to be a hater. It's safe as long as it's a pedophile but on the contested areas it's a crapshoot of public opinion whether you're reasonably taking a different "political" position or you're a bigot.
Personally I think prop 8 voters are bigots. And I will give a rational explanation for why incest and gay marriage are different for example:
1) Gay marriage, no kids.
2) Incest, genetic mutants
1) Gay marriage, most likely minor power differences.
2) Incest with children/parents is fraught with psychological manipulation and questions of consent.
Group marriages aren't morally wrong but they would produce a completely different legal structure since they would have to be framed after a corporation. Divorce isn't the same when a fraction of the property has to be split off. It might be legal some day but it's going to have to be a separate legal framework. It would be impossible for 5 people to have the "same" rights as 2 people. They would by definition of the arrangement have to be discriminated against. Without breaking the laws of physics you can't give them the same rights.
The fact that there are perfectly sensible reasons for discrimination is the reason it's in my books 'justifiable' discrimination. The proposed justifications for gay marriage are: "It's gross."
Just saying "It's gross" isn't a reason to discriminate. Therefore it's bigotry.