If he's lifted them then he's an idiot, but it's not like he's a renter, if injury resulted it'd be no ones fault but his own. The people around him don't have any obligation to try and convince him otherwise.
Obligation.....no, but if I was watching him play and saw him lift his mask I would shout at him, its like when peeps walk off a field and forget their barrel sock ( which we have all done!) I hope that when people notice that they would say something quick!!