Are you going to destroy them by flaming?  Isn't it a better idea to present facts, address their questions, and try to snag some fencesitters?  Don't make yourself an enemy.

Oh, by the way, these are hard targets.  The Million Mom March and HCI are pus...um, pushovers.  They are lightweights.  Their antigun stance was an opinion divorced from the rest of their ideology.  Simply presenting facts about how assault weapons function the same as all other weapons, or how the choice of the criminal was whatever gun they could steal, and they weren't going to go through legitimate sources to get them.
But now, when you post links to that hippy BB, and others, you are committing yourself to either decisively using weakness in their worldview to get thing to think outside their self-imposed box, or you are committing yourself to getting fragged.  They have a cohesive, coherent worldview, well thought out and well organized.  They have the facts to back up their opinion, and they know how to present it in a convincing manner.  You must know them well, to be able to do anything with them.