I would have that entire topic shut down now, this is the wrong format for this debate. If you have the time go in prior to class and have a meeting with the teacher and principal. Inform them that this is a topic that you will not tolerate as it goes against your long standing culture of hunting, fishing, and proud Canadian military heritage. This is not a topic that a teacher should be approaching in class, and could very well alienate your daughter and subject her to ridicule and bullying based off of her beliefs. Alienation and bullying by students, and in this case it could also be the teacher (been there and stood my ground with snide anti teachers before), is frowned upon and in this case being against her personal beliefs could turn out to be a personal attack manipulated by the teacher. If this went any further I'd be calling for her job and that of the principal.
Go in if you have time and raise hell, it's far better than a phone call.
May I ask what the class is in order to get better context on why they're having the "assault rifle" debate? Perhaps if the teacher were to divide the students equally and have them debate the pros and cons based off of research instead of allowing a 31 to 2 debate this could be allowed given it's in the context of the class and makes the kids use their brains and learn to research. This format however is plain and simple division and conquering and has already gone too far, I'd shut it down if I were in your shoes.
Still this is a good opportunity to educate your daughter that there is no assault rifles legally owned by her father or allowed in Canada.