I think it's totally fine
What's different about them to have an opinion.
To each his own
Love is love
So long as everyone is a consenting adult human I have no problem with it. I am not gay, but I didn't choose to be heterosexual. I can only assume most people do not chose their own sexual orientation.
I believe in equal rights. If I have the right to marry who I love so should everybody else. It doesn't matter if I think it is wrong/right - I have control over who I love and who I marry, and so should everybody else.
Im cool with it.