(For a beside-the-point point next to yours, I'll note that it's not just conservative Republicans we have to worry about inciting to war.) Anyway, I guess I'll repeat myself and expand the "et al.":
Meanwhile Canada et al. are free to do as they wish since they're not in the position to actually start something with Iran, and their words are just words.
I'm a US citizen, I speak out against these things as much as the next guy here (which isn't terribly much, I don't claim to be an activist). I have a lot of opinions I like to push for with varying strength, some very unpopular. One of them is that the US government shouldn't be speaking out and condemning Iran's decision to execute this guy. I'm not trying to shut anyone up personally (though I suppose by proxy I do want to shut Obama up personally (or anyone in the US gov. with a lot of clout) because it's so easy to uncharitably interpret his thoughts as official US stances); I am trying to dissuade an official condemnation from my country for reasons I've already mentioned. I didn't even mention a secondary consideration that the US does many of the same things and worse, albeit on a much smaller scale, and because of that one could argue it should condemn itself before condemning others. But that's also beside the point, and to me it's a weaker argument.
1. we should not ever attempt to defend people being abused until we erase all vestiges of abuse from our own country or at least 'condemn ourselves',
2. saying that it's bad that some country abuses its citizens is going to contribute in a small way to the potential for starting a war with a country who continuously flaunts its nuclear program in the face of every international body that opposes it and threatens our allies with total annihilation, so we shouldn't make them upset,
3. Canada's words are empty.
You seem to have an unrealistic view on our relations with Iran. You seem to think that us complaining about the unfair treatment of its' citizens will make them more likely to threaten war. This is not really the case. They could give a shit what we think of how they treat their citizens. What they do care about is our continued insistence that they not be allowed to develop nuclear weapons. That and the pressure of the international community imposing sanctions on them makes them pissed off.
As you said, condemning them for this is a relatively minor thing. So minor that they will probably completely ignore it; it has no bearing on their nuclear operations or their arms deals or their not-so-secret terrorist war with Israel. The only way it will even pop up on their radar is when their international partners mention it as a concern, because we're concerned. Again, this does not inspire them to go to war, but it makes them realize they have to be more careful about how they abuse their citizens, which in effect does some good.
Finally, for the previous reasons Canada doesn't have to "start something" with Iran. Most conflicts between nations are not dealt with by their military, they are dealt with by sanctions. Our military leaders have stated time and again that it's the only practical thing we have to deal with them at the moment. Canada has resources and influence which may apply here.
Meanwhile Canada et al. are free to do as they wish since they're not in the position to actually start something with Iran, and their words are just words.
I'm a US citizen, I speak out against these things as much as the next guy here (which isn't terribly much, I don't claim to be an activist). I have a lot of opinions I like to push for with varying strength, some very unpopular. One of them is that the US government shouldn't be speaking out and condemning Iran's decision to execute this guy. I'm not trying to shut anyone up personally (though I suppose by proxy I do want to shut Obama up personally (or anyone in the US gov. with a lot of clout) because it's so easy to uncharitably interpret his thoughts as official US stances); I am trying to dissuade an official condemnation from my country for reasons I've already mentioned. I didn't even mention a secondary consideration that the US does many of the same things and worse, albeit on a much smaller scale, and because of that one could argue it should condemn itself before condemning others. But that's also beside the point, and to me it's a weaker argument.