Following up on this, stuff from about ten years ago. Shit our hero has been willing to sue people for defamation! (Bolding is mine)
After Harper became Canadian Alliance leader that year, he participated, along with current Conservative election chair John Reynolds, in a very public campaign to pressure the nominated candidate in the riding, Ezra Levant, to step aside so he could run for a seat in an upcoming by-election.
At the time Reynolds said that the party would assist with any debts [Levant] may have had which media reports claimed were at least $120,000. (Calgary Herald, March 22, 2003, National Post, April 8, 2002)
The incident deeply divided party members in Harper's riding association resulting in Levant and three other Calgary party members filing a $5.8-million lawsuit against other party members and executives over alleged defamation related to the nomination battle. (Calgary Herald, November 22, 2003)
There's more on the same set of incidents (I think) from this old FreeD post from back in 2003. I won't describe the contents through the link, just point to them, because doing more might itself count as defamatory these days.
And more shit from WK's old site. Ezra tried to sue Chuck Strahl?
PS. Thanks to Holly Stick in the comments!