In practice

It's disturbing to actually see floor-crossing legislation enacted.

In theory, it was all fine and good to talk about floor-crossing legislation, but the NDP government of Manitoba is actually trying to make it law.

Now of course the Canadian first-past-the-post electoral system is deeply flawed in that voters are simultaneously asked to cast judgment on candidates, parties and party leaders, but that is the system that every province (and the federal government) still uses, and as long as that system is still in place, anti-floor-crossing legislation is deeply undemocratic because it gives more clout and power to the party system, essentially making MPs less representative of their constituencies.

Because it's impossible to gauge the extent to which voters balance the three factors before them as they vote (candidate, party and party leader) it's silly to make the claim that a particular constituency voted only for a particular party when electing a particular candidate. The reason the Liberal party did as well as it did in the past election was because of how many incumbents it had and how many of those incumbents had ties to their communities. There's also much emphasis placed on "star candidates" and their ability to secure more support than their party could ever manage by itself. Basically, candidates matter.

And unless and until Canada goes to a system that is based solely on choosing a particular party instead of choosing candidates (i.e. proportional representation), MPs should be able to floor cross whenever they feel like it. If enough of their constituents truly did mean to elect their party and not them as individuals then that will be known at the next general election. Canada has mandated elections (which happen less than 5 years apart), but too often people forget about that.