There's a difference between opposing such things respectfully, and proudly proclaiming in public you believe gay marriage is equal to incest, polygamy, and pedophilia.
If one believes that same gender sex is immoral, then it would be hypocritical for one who holds that position to not equate it to other sexual activities they view as immoral.
As for myself, while I don't acknowledge the equation to incest and pedophilia because they are activities that it is essentially impossible to argue involve all parties involved engaging in informed consent to. However, equating gay marriage to polygamy is perfectly reasonable, so long as the individuals involved all consent to the arrangement. I ask you, since you seem to favor treating the two differently, on what basis do you find gay marriage acceptable and polygamy as unacceptable?