The huge problem is that geographical borders don't nicely line up with cultural/ethnic/attitude borders. Let's say you let a province (or US state) secede over political/cultural issues. What happens to all of the people who don't want to go along for the ride? They're now at a huge risk. Those dissenters might even be persecuted or, at worst, cleansed, depending on the laws of the new seceded country.

So then you say, ok let's do it by county (or whatever the Canadian equivalent is) instead. Same problem. Even within a county-sized area, you're going to have dissenters who are at risk in the new country. Even within a single town. You can't draw geographic borders around and write laws for swiss-cheese-shaped clumpings of individual people.

I live in a pretty "red" area in a "blue" US state. If Team Red decided that half of my state (including my home) was going to secede into their own Red Utopia, my family would legitimately be in fear for our lives. I don't think secession is ever going to be a viable option in the real, polarized world where political beliefs are peanut butter spread across the geography.