Well they don't use their power to go after trivial criticism. But if you criticize immigration policy, you're probably headed for the slammer.
Obviously, you haven't heard of the recent fiasco with Immigration Minister Judy Sgro. Her immigration policies were harshly criticized by, well, basically everyone. None of those people were jailed, and, in fact, they were applauded for helping to expose a really bizarre policy that really needed to be changed.
And, no, tons of American citizens are not being held "without trial." There are terrorists being held, though the number isn't overly high, and the couple that are American citizens have been ordered charged or released by the courts.
For the vast majority of them, no charges whatsoever have been laid. If you're so sure they're terrorists, why can't you charge any of them with anything? If there's inadequate evidence, how do you know they're terrorists?
There are indeed US citizens, as well. Look up the name of Yaser Esam Hamdi, a US citizen who was held for two years as an "enemy combatant".
As I said before, they're being held there because they're allegedly "a threat to national security". That sounds familiar - it's the same reason given for deporting Zundel.
The US is far, far from perfect, but it's also one of the few countries to take freedom of speech seriously. Canada and Germany sure don't.
The number of people who get arrested who take part in protests against the government in either country is comparable, with usually less Canadians arrested than Americans.
I can go to Parliament right now, stand outside, and scream obscenities at it and I probably wouldn't get arrested. I'd get looked at weird, but not arrested.
I can do anything I want within my house and the government won't tell me otherwise.
I can write a letter to my editor criticizing anything I want about the government and I won't get arrested for it.
I don't particularly like our hate speech laws, but that's just one segment of speech. If you want to generalize that to the entire country, be my guest, but you'd be, well, wrong. Canada has a (1, 1) rating from the Freedom House, which means that it's equivalent on the large scale of things to the United States in terms of both political rights and civil liberties.
For the record, Germany gets a (1, 1) rating too.
You're taking small, isolated events that are, while reprehensible, not in any way representative of the grand scale of things, and then trying to extrapolate these events to the country at large. It just doesn't work.