Could you explicitly quote which things our PM says publicly about Trump that he should keep to himself?  I don't remember anything so please remind me!  (The straight-talk of Merkel seems to be more undiplomatic, if you insist on using this word.)
As for TPP, Trump already says he will cancel it the first day of his office (i.e. it's going to fall through).  Seeing this, any prudent PM would be looking for alternative strategies.  I am sure if Harper was still in power he'd done the same too!