More on Ryan Warawa's Troubled Candidacy

One of the neat quotes J-Rad plucked from Conservative Candidate Ryan Warawa's most disturbing blog today was:

I wonder how many Liberal memberships [disgraced provincial Liberal staffer David] Basi offered to buy [Keith] Martin with the Basi Boys’ drug money.

This passage from Canadian Press explains that one:

Ryan Warawa, who's running in Vancouver East, suggests in a 2004 blog post that Esquimalt-Juan de Fuca Liberal Keith Martin had ties to a former B.C. Liberal cabinet aide now on trial for corruption.

Keith Martin's response to this:

Martin had not previously heard of Warawa's blog - nor of him - but said now he considers the comments slanderous and libellous.

...which was my impression too. So: does Stephen Harper allow his candidates to libel the other side? If not, why is Mr. Warawa still a candidate?