Progressive Overkill

Salon traces back the origins of the Cordoba House-Ground Zero controversy.

Although I have no idea what the opening sentence means:

"A group of progressive Muslim-Americans plans to build an Islamic community center two and a half blocks from ground zero in lower Manhattan."

Aside from I'm not sure if "Muslim-Americans plans" should be both plural, why did the author add the word "progressive?"

The word progressive is becoming a little over used these days. I hate the fact that on group of people claim to be more "progressive" than others. Talk about presumptuous arrogance. In the context of the article, what exactly makes them "progressive?" It wasn't explained. Is there such a thing as progressive Christianity and would the left ever admit to it? What was the author trying to convey or even influence by constructing his sentence that way? That he's soooo prog in his politics?

Salon: You're really progressive Commentator!
The Commentator: What do you mean I'm progressive? How am I progressive? I'm here to amuse you with my progressiveness? I make you laugh because of my progress? How the fuck am I progressive?"
Salon: I don't know. You're just, you know, progressive. A progressive guy.
Larry the Monkey: Take it easy, T.C.
T.C: No, I'm not gonna take it easy. Salon is a big boy, he can fend for himself. How am I progressive? Because I blog? Maybe I'm fucked up but am I a progressive clown?
Salon: T.C., you're really making it bigger than it really is.
T.C.: Jesus Christ, how am I fucking progressive? You said, I'm progressive..."
Salon: Get the fuck outta here!
T.C: Ha, ha almost had you! Me! Progressive. It is to laugh!