You are something of a numbskull.
First, you want some evidence that Harper left the PC's over Mulroney.
Easy. Here:
http://en.wikipedia.org/wiki/Stephen_Harper#Political_beginnings
But recently, he's been praising Mulroney's term as Prime Minister and has been personally chummy with him. Why would he be praising Mulroney when at the time he was so disillusioned with him that he quit the party?
Last week Harper was claiming calling an inquiry was so "dangerous". Now he's called an inquiry. (Where was the danger?)
I've no beef with Mulroney. He was cleared of wrong doing. New information seems to indicate he lied. Wouldn't surprise me if he is found guilty of something - he brought a used car dealership salesperson's approach to Canadian politics, but my comments weren't about Mulroney. They were about Harper.
Harper is a big pontificator, but on a whole series of issues he's showing himself to be a manipulative, morally hollow person. This was just one example of it. He befriended Mulroney because it suited him at the time.