Or: important considerations before even rightfully tearing into some abysmal person who lives in a jurisdiction with UK-esque defamation laws and which has mechanisms for enforcing their civil judgments in your jurisdiction.
NOTE: I am not yet a lawyer in Canada, let alone in the UK. This is not actual legal advice, but rather an extremely basic summary of why people often just fold and post some kind of apology when a vindictive Brit comes after them with lawyers.
Basically, in these contexts, the burden of establishing the truth of a statement that's prima facie (on its face) "defamatory", when a claim of defamation has been made out to the court to a level that they're willing to let the plaintiff pursue the claim, falls upon the defendant. Which means, one needs to convince a judge that it's more likely that the requisite threshold of truth is met by the statement in question than that it isn't. For a lot of statements, like ones that make arguments as to the effects of someone's speech, especially when they outwardly deny having some given goal? The defendant will probably want expert witnesses to help out there, which is, to say the least, expensive.
Even if you do that? That's not necessarily sufficient. A judge is totally at liberty to, based on the evidence that's been presented to them, refuse to draw what seems like an inference that's impossible to not make based on the evidence that's been presented. Judges are totally able to look at decades worth of social science and statistics and all that, and just say "well lol no; source: lmfao". If, rightfully, you have a problem with that? Your only recourse is, at great cost, appealing the decision, if the appeal court even gives you leave to appeal.
So caution might be warranted when making fair statements about awful people who could potentially have the protection of aggressive defamation laws on their side.