Conservatives think that the current system is fine. No problem with the government doing whatever they want. They have a mandate, after all. 

But the Liberals, who won "fair and square" under their preferred system don't have a mandate to implement their platform. Logic is not a conservative's strong point.

"But, but, but.. this time it's different!" Does a government with a mere plurality get to do what they want or not?! Right now they do. But the first thing they should do with that power is eliminate that power.