Actually, they do, as a matter of fact.
Sure, it's not large enough to allow for power usage like that of their Toa counterparts, but canon Matoran also eat by absorbing their element, making it just as essential as wearing a Kanohi (though, admittedly, they do this much less often than that of an average human), since they both provide them with the energy required to keep them constantly running around the MU.
So theoretically, if they end up pushing themselves to the point of exhaustion, or otherwise aren't able to replenish it, it should stand to reason that these reserves would eventually run out at some point as well.
Agreed on both counts.
I'd imagine that said negative emotions would be just as capable of bringing their wielder into Anti-Hero or Anti-Villain territory, though. Might depend on how frequently they end up being used, and how often they actually give in to them.