The most effective way to counter stereotypes is to show just how stupid and wrong they are by providing counter examples and exposing their hypocrisy.
Telling people they want to be married too and disagree with somebody who says they shouldn't does nothing to combat the stereotype that their marriages would somehow be "different". Instead of just pleading and even begging for equal rights they have done something better. They have pointed out that the stereotype about gay marriages being"different" or not as authentic as heterosexual marriages is patently false. They've provided a great counter example of a straight marriage falling to pieces regardless of its supposed sanctity.
The obvious and logical conclusion is that since heterosexual marriages fail all the time then it must be the people involved and not the act itself that makes it a special union. And thus, if the act isn't that important (but in contrast, the people are) then there is no reason to forbid gays from marrying.
The message was quite effective. Good for them for being creative and thinking out of the box in an effort to actually get their thoughts heard.