Here is my modest proposal: take a breather from organizing big, confrontational street protests for about a week. Announce you are doing this so that anarchist fish that swim within your sea of students cannot hide themselves, at least for a week. This would show that you care about Montreal and about Quebec and not just about yourselves. Yes, it would take some steam from your movement, but it would demonstrate a real interest in doing what is right for Quebec.
As it stands now, it seems as if the groups doing the organizing do not seem to realize that putting hundreds or thousands of people on the streets might not be just a bit problematic at a time of escalating violence. The only way to de-escalate is to do less. Condemn the violent actors, be creative in organizing protests where the possibility for violence will be minimized (including violence conducted by the cops), and seek other ways to persuade the public of the rightness of your cause.*
* Of course, I do not support the tuition protesters as I have repeatedly protested here. Still, I do believe that they have a right to engage in dissent. I just want it to be thoughtful, peaceful dissent that does not provide provocateurs with more opportunities.
The real risk of continuing on the present course is that the groups will alienate the rest of the province--those that have thus far not been alienated.
On a related note, I agree with Don Macpherson that Pauline Marois has painted herself into a corner: that by adopting the red square (symbol of the tuition protesters), she now either stands with the violence or abandons the students. I am perhaps more openly gleeful about this outcome than Don, but perhaps not.