To put it more generally, the "Gish Gallop" is the phenomenon where a denialist -- whether it be a Creationist, an anti-vaxer, a homeopath, a 9/11 truther, a Holocaust denier, or whatever -- can throw out fallacious arguments, or even make up facts out of whole cloth, faster than any rational person could possibly rebut.
At the vaccine meeting, there were a number of claims made which I was almost certain were either completely false, or else a misunderstanding or misrepresentation of some other fact. Some of them I was able to rebut in real-time using my enV2, which has a totally shitty web browser, so if I can rebut your claim using that thing that's gotta tell you something... but for the majority of these claims, I just had to maintain a skeptical posture and move on.
I suppose I could have just made shit up too, but ultimately that undermines the whole point. I am not an activist, I merely can't stand when people make statements that are false or misleading. I suppose a pro-vaccine activist might lie to promote vaccines, but that is not my agenda. Can I lie in order to insist on the truth? No. It is inherently self-defeating.