My first comment was removed for breaking Rule 1. Be Civil so with the clarity of hindsight I've toned it down to what I think is an acceptable level.

YTA.

He is your boyfriend, you love him, he's afraid, and you're not being supportive. You're supposed to be on the same team and looking out for each other but you're throwing him under the bus and it's not very nice.

Yes he lied, that's not acceptable. But he's been afraid of being accepted his whole life. He's been afraid that his family won't accept him for being gay, and he was afraid that you wouldn't accept him if you knew he was in the closet.

I am gay and from a well receptive family and I was deeply afraid of telling them. My boyfriend was from a less accepting family and he was afraid also.

You brushed off a comment he made about you being from a "cool hippie San Francisco family" which may have been insulting to you, but it means that while you might think that being gay is no big deal, it really is a big deal for other people. Nobody else lives their life from your perspective, only you do.

When his parents leaves and you want to be angry at him, go for it. He lied to you. But please don't out him to his parents. That's not fair.