It's more the whole peaceful protests, someone may be involved in a protest they don't want people to know about. Say someone is at a gay pride rally, people could use that against them. They might not want to be identified by everyone.
You're not really showing Gay
Pride if you're scared of showing your face at one.
You might as well not go, if you're going to wear a ski mask.
I don't see a real reason why anyone should need a mask at a peaceful protest.
If you go there in the aim of peacefully protesting, then why wear a mask?
And the Gas Mask thing may be a valid point, but really, how many people actually have access to Gas Masks, and how many people actively bring them when they go out to any sort of protest or rally?
If people are in protests that turn sour, and then run home to get a gas mask, then they actively know they are returning to a riot.
Are you expecting to be tear-gassed and attacked by the Police?
If so, you're probably expecting some form of provokation to occur, such as violence or aggravating actions.
In which case you're probably not going to something that you expect to be a peaceful protest.
I'm not saying that protesting shouldn't be allowed, but there are too many people who go just for the sake of trying to start a fight or riot. People actually enjoy that.
And then other idiots get all rowdy at the fact that the Police may be present at a protest.
Of course the police will be present! There's a large gathering of people in one place! It is very likely that accidents may happen. The police are there to try and help and prevent that, aswell as ensure that Traffic doesn't get clogged by protesters. If you're going to go and insult and shout and threaten and throw things at the Police for that, then you shouldn't be going to a protest.
As far as I am concerned, there should be little to no reason for anonymity within a protest.
If you want to protest, then you have to put your person behind it. There's no point trying to give voice to an invisible person.
And if it goes sour and turns into rioting and looting, then masks are just going to help people commit crimes without being caught. If you catch someone after they've looted and rioted and you can charge them for it, then I'm happy if you can also slap on the charge of being masked.
And while I'm not Canadian, I personally would respect a law like this in my own country, a place where mass riots caused death and destruction, burning down houses and shops alike, in the Capital and other cities around the country, including the city that my family lives in.