The issue wasn't that they were arrested or even charged of anything. The issue is that the government deliberately used the emergency act (which is basically a nuclear bomb) where they could've simply... arrested them. There was no emergency, there was no widespread unrest or any event that was leading to a loss of control. They could've absolutely just arrested everyone, using force if necessary, and moved on. The protestors weren't even armed, they could've just used anti riot police like they always due. As you said yourself, the UK protestors were arrested without using the equivalent of martial law.
So my point isn't that the protestors were innocent, it's that Trudeau's government clearly used the emergency powers act as a way to send a message, and to show that you won't just get arrested but also stripped of your rights completely. Which is to me absolutely abhorrent, and that's coming from someone who actually volunteered for Trudeau's campaign back in 2015 and the election after that one.