I've heard this argument, but the glass closet is bullshit, and it always has been.
Let's look at this specific example here, because this is not saying "Hey Jimmy down the street likes boys!" We've got a grown man here that advocates and profits from promoting homophobia (as evidenced from his very public positions and votes). That same man then turns around and says "Hey, I'm going to be as public in DC about being gay, because the dipshits back home, can't see it." Now everyone in DC that is cool with institutionalized hate, turns a blind eye, because at least he's keeping' the homes down. and everyone that believes in basic human dignity turns a blind eye and says, "Gee if we say something, it might cost him his job of trying to keep institutionalized hate. We better not do that, let's just dance to Erasure some more."
But hey, the glass closet worked Ken Melman, and what did he give us, besides homophobic constitutional amendments, and another four years of Bush.
Trying your damnedest to keep homosexuals second class citizens is a dick move.
Hypocrisy is a dick move.
An elected official playing his constituents for a bunch of rubes is a dick move.
So fuck him. Fuck the glass closet. And fuck those that promote the glass closet.