The only question as to what would happen to them if they did would be how many pieces would their respective members be torn into.
NAMBLA, however, did march in "Gay Pride" parades until it was realized that this generated bad press. Now they participate without their banner.
As documented in The Overhauling of Straight America
"A media campaign to promote the Gay Victim image should make use of symbols which reduce the mainstream’s sense of threat, which lower its guard, and which enhance the plausibility of victimization. In practical terms, this means that jaunty mustachioed musclemen would keep a very low profile in gay commercials and other public presentation, while sympathetic figures of nice young people, old people, and attractive women would be featured. (It almost goes without saying that groups on the farthest margin of acceptability, such as NAMBLA, must play no part at all in such a campaign; suspected child-molesters will never look like victims).
You'll notice that Kirk & Pill didn't say that NAMBLA was unacceptable.