So they don't agree with the guild position/decisions/style, they change to a different guild, and you think this is a bad thing? Simply being your friend doesn't mean they have to agree with everything you do, or be in the same guild.

I mean, you're paying for their account, so what you do with that is your choice, but it doesn't sound like they actually did anything wrong, so to cancel it for the reason above would be fairly rude.