You might find Michael Warner's The Trouble with Normal helpful here; the first chapter ("The Ethics of Shame") does a nice job of explaining why monogamous privilege and straight privilege don't look all that different to me. Unfortunately, it's U.S.-centric in its examples, but I hope that won't be too irritating.

Careful with that book, though -- it might make you more radical than your LGBT friends, and wouldn't that be annoying? ;-)