"feels especially odd..."
I think you're confusing what your gut tells you to feel, and what the law says. 
The question isn't whether what he did was icky, the question is whether or not he committed an offense that justifies his removal from office. 

"That would be no different than a school teacher hinting at better grades in return"
Of course it would be different. One is a powerful man and some people are attracted to power. The other is a person in a position of authority using coercive power to essentially prostitute the student for grades. If you really think those things are the same I think you have a serious critical thinking problem. 

What he did was gross, and I don't like it. But Maxime Bernier left top secret documents at his call-girl girlfriend's place, which is super icky and also an offense, and he's running for the tory leadership today. Saying "it's gross" is nowhere near to being a logical or helpful response.