Trudeau has no choice but to refrain from saying anything against Trump, because Canada has to do its best to  get along with the US government, like it or not. 

Incidentally, Canada's situation in relation to the US reminds me to an extent of when I was in Portugal and I asked the tour director on our bus trip how his country gets along with Spain.  He said the two countries get along ok, and I then pointed out (and he agreed) that  Portugal has no choice but to do so, since Spain shares its sole land border. Well, that's pretty much what our position is like with the US.