As far as Islam is concerned, people usally convert in it in order to avoid all sorts of physical abuses -- mental abuses is not much of worry for "infidels." As I've already said above, nothing can't be undone. What the forceful converted guys can do in this situation is to send to hell all the process of conversion, which is in Islam is a merely mumbling of one sentence (hashhadda). Practical advice to all forcefully converted infidels: Say what you are forced to say and, a second later, when you step out the door send all the process to hell. Who can prevent you being who you are?!
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from the article: Gaza Christians protest 'forcible conversions'