"Comrade Akhmetshin is clearly a Russian spy. That's the point of the article."
The article doesn't come close to making that point. You've fallen victim to bias confirmation.
"The Russian wasn't offering inside dope on the anti-Putin lobbyists, but was hoping to stir the pot."
Making an innocuous and rational suggestion is not stirring the pot. If he had offered sketchy information, it could have been suspicious. And if you had a contact for a popular Russian news outlet and was concerned about potential Russian sanctions against Canada, would you not use the contact to make a similar, or greater appeal?
"Why should Freeze have followed up by fact-checking his colleague?"
Because that's what objective and truth-seeking people do. Presumably, that's also what journalists should be doing. Having not done so puts Colin Freeze in the position of having nothing to say or opine on the matter more than any random person.
It sounds like you have a conclusion in search of evidence.