The not-so-Disaffected Lib is trying to smear Thomas Mulcair by claiming he's a traitor for not backing the Liberal party in the recently-announced Quebec election. That sounds like something the Conservatives would say, like when they called Jack Layton “Taliban Jack” for opposing Canada's involvement in the war in Afghanistan.
Mulcair is a staunch federalist. He opposes Quebec separation and another referendum, which he said Quebecers don't want. It's his job as leader of the Official Opposition to promote federalism and oppose a referendum, which he is clearly doing. It's certainly not his duty to support the Liberal party, which he is not a member of.
Let's leave this kind of mudslinging to the Cons.