This means (), or "(Your comment) sounds as if it's (about) someone else's problem (although it actually is not)". Here, MC is saying he himself should be suspected and refused, almost like he isn't interested in defending his own position. The leader pointed out such a behavior is unusual.
So, interestingly, although the literal meaning of this is "It's someone else's problem", its actual implication here is "It's _your_ problem". is commonly used as part of (), so just saying can have the same implication.