The point I keep raising is, what do you mean by Truther? Do you mean anyone who raises questions about 911 conspiracies? Or do you mean people who actively do something about it about it?
If you focus on the ideology of 911 conspiracies, instead of just talking with whacko right-wing Americans, you probably have a very different picture of what's going on. Whacko Americans are very receptive to this idea. There would be zillions of Americans who do not necessarily belong to a 911 conspiracy group but who see the world in terms of conspiracy and perceive this 911 conspiracy stuff as somehow reasonable. I suppose what I'm saying is that 911 conspiracies have become part of 'mainstream' conspiracy theory and are now found clustered inside of all kinds of other conspiracies - Holocaust denial, Kennedy assassination, Anthrax, Floride and Aspartame. There is almost no one involved in 911 Truth at any level who is not part of this world of killer conspiracies.
Truthers out there are no longer trying to convince those not already part of this world but are rather trying to hook up with other kinds of conspiracy theorists and convince them to incorporate 911 Truth into their repitoire of conspiracies.
We Are Change holds demonstrations in New York at Ground Zero every year. The number of people they attract gets smaller every year. Last year there was about 100 people and this was drawn from a national group. Some of the demonstrators came from Georgia and Ohio. In fact, it is pretty much the same group of people year after year - they just get tighter and better organized.
If it is true that hundreds showed up for DRG in Montreal, this would not be so strange.
This video from 2 years ago shows a large crowd and may just be the same people. Montreal is next to the US/Canada border and I wouldn't be surprised if many are Americans.