Sure, but it depends, you can't put a black bag over everyone's head
You don't need to. Horizontal tyranny. Fear works the same way endorsements work, but in reverse. You blackbag one and people lose their nerve. Protesting without any perceived cost and protesting with fear of loss of life/torture are two very different things.
and it's not worth it for people who are just campaigning for something like no war.
No one has ever been more reviled by the state than the peacemaker. See Christ, Jesus ; Martin Luther King ; Gandhi
I could agree in the US (not familiar with Canada's political system, so I can't compare to there), where the number of people voting is so incredibly diluted in comparison to the people in power - here though, most people are at most a 20 minute drive from their local MP's front door, and it would be pretty easy to talk to them (no fancy offices), so I think here at least, campaigning to your MP can make a difference (well, for issues like war).
Voting is asking for permission. It's requesting something. It's a fundamentally weak position. The only time politicians respond to it is when their own political power is threatened. I can't speak for the UK, but certainly in the US, politicians are not usually funded by their constituents, but by special interests and so the values and interests of their constituents is irrelevant.
Also, the system is fundamentally corrupt and immoral. Why participate at all?
I see this differently than most people, even most people on WF, many of which are fairly enlightened and radical. Politics is a charade. A dangerous abstraction. If you "believe" in it, then it is "real". But it is not "real" if you choose not to believe in it. It's just another delusion, people adopting titles, masks, uniforms and pretending they are something they are not, in a system that is arbitrary and irrational.
I can't participate in politics because I see it as the sad farce it is. I speak political language and engage these debates because sometimes I like to socialize with my fellow monkeys, but that's as far as I am willing to compromise. I refuse to pretend I believe in something that is a lie, something that produces much more bad than good, because if I pretend it is real, it will validate my values.
That's how I see it anyway.