Speaking from experience, they're going to be on good behavior around you and others. It's what happens when they think no one will notice or no one will hold them to account when real discrimination occurs.

I've met plenty of people who claim to be LGBT supporters in public, but have no problem harassing LGBT people, discriminating against them and calling them slurs when they think no one else is looking. Same thing goes for people in power, like bosses and owners, or police and judges. Discrimination doesn't always look like American History X or the Westboro Baptist Church, the vast majority of it is low key and insidious.