Instead of bashing politicians who cross the floor, we should instead be more like them.
It's more likely than not to be a good thing that people change political parties. First it shows our competing ideologies are similarly moderate and not extreme; second it shows that we aren't as polarized and as dysfunctional as other countries are; and thirdly it proves we balance principles with pragmatism.
Of course changing parties can be done for selfish reasons, but so can any good deed. I want a moderate political system where compromises are made for the good of everyone. If selfish people help achieve that, I'll be selfish too and applaud it.