I would hope you are right that "The question would be one of evidence and how the discussion was framed."

However, the Canadian Bar Association seems to think it would depend on whether the professor's teaching constituted  "unwanted, persistent behaviour (physical or verbal) that offend[ed] or humiliate[ed] individuals on the basis of their gender identity or expression." 

So they seem to think it would depend on how offended people get. And it doesn't help that Human Rights legislation (as I understand it) already defines sex and gender as independent categories.