A bullshit excuse used by conservatives and the religious right to justify using their beliefs as weapons to preach against others who don't believe in what they do. They claim that their right to speech (hate and discriminate) against anything they find immoral or against their ideology should be protected and legalizing something like abortion or same-sex marriage would infringe on their rights and hurt their "religious freedom" (to hate).
Tom: So how's everything going?
Mike: Pretty damn good. I'm very happy.
Mike: Yeah, Scott and I have been together for almost 6 years now and it's been amazing. I love him.
Mike: I think I'm going to ask him to marry me.
Tom: WTF? That's fucking gay!
Mike: ...Well, we are gay...
Tom: That's so wrong and nasty. I'm offended. God hates that gay shit, and it's my religious freedom to not put up with your sin.
Mike: ...I'm sorry you feel that way. We're not going to marry in a church. The county is going to marry us.
Tom: Fuck that. That's wrong and I don't agree. Don't forget to send me an invite, faggot. I'm going to be there with my posse to protest that shit. I'm a christian and you can't force that gay shit on me.