I can't be the only person who first read this as defecated and was a tad confused.
OT: Probably try and understand their reasoning, and make a decision based on that. Then again I'm not a nationalist at all so I'd probably just go with them if I loved them enough, not that I'd give a shit about the nation I'm moving to either.
This question is not really about them (imo). It's about me.
When my friend, partner, somebody I hold close defected to another ideology (as in become a chinese or whatever), I certainly would be told long before the actual transformation, or as in your words defection. So we would talk, I certainly would think about it, question why somebody I certainly see as an inteligent person is changing his ideology, defection or whatever. It could actually be just an introduction of some sort of faith, as everybody in my close circle is either agnostic atheist, apatheist or strong atheist (some meds, vets and other science educated people). After "the talk" I would either be convinced by their arguments, or wouldn't.
Then I maybe would move, defect or whatever, if my current partner supported it (as I value her opinion in such regard) and if we wouldn't eat dog shit on the streets yo feelin'.