Why Open Primaries Suck
When I say that I oppose open primaries it's because of things like this.
The Democratic nominee should be decided by Democrats. The Republican nominee should be decided by Republicans. The process should be free from manipulation by people who aren't committed members of either party.
I agree that it sucks to be a non-affiliated voter in those situations. But the solution to that problem (and the more general problem of the two-party monopoly) is instant-runoff voting.
Open primaries just make being a party member meaningless.