"Alpine perch": did Bob Rae compare Harper to Hitler?

Dan Gardner just tweeted this:

Did Bob Rae really use the term ‘alpine perch’ to compare Harper to Hitler? I have a lot of respect for Dan Gardner but I wonder if this time he’s stretching it a little thin. I did a quick Google search on the term and didn’t find any references to Hitler, even hyperbolic examples.

Dan Gardner is at times inscrutable. Was he joking or was he being serious?