Yes, but it depends what one conceives the role of an MP to be. It's true that an MP represents a constituency, but Parliament's rules suggest that all MPs represent all Canadians, it has never accepted that an MP has to do what constituents want. Quite apart from the problem of finding out what that is on any particular issue, it must be obvious to anyone that not everybody in a constituency thinks the same way. Every constituency, for instance, I'm sure contains a mixture of pro-lifers and pro-choicers on the abortion issue, no MP can represent both sides of that and it's unreasonable to expect it. Pick any issue, there's certain to be a divergence of opinion in any constituency, MPs can represent only one opinion: their own.
The party system does a certain amount of violence to that ideal, but I think it's a very bad idea to destroy the principle. It's a violation of the traditions and privileges of Parliament to try to bind MPs as that private members bill suggests. MPs must be free to cross the floor if they wish to, abandon a party they signed up with if they find its policies have become odious to them, but really, the reasons don't matter. It may be crass opportunism, as Belinda Stronach's defection appeared to be, or it may be a highly principled decision of conscience, and I don't think we should take that latter option away from them. They'll have to face their constituents in another vote eventually, assuming they run again, I don't even see the need for a by-election, since most MPs in our first past the post system are not elected by a majority of constituents anyway. Elections may be where the voters speak, but what they say is often garbled and incomprehensible.