^Yeah, but abusive parents "don't mean to" hurt their kids either, or at least they don't think they do. Some people love, but love badly or corruptedly. I mean, come on, realistically, anyone in that room could've been hurt or killed by shrapnel from the explosion, regardless of their position. (Hell, realistically, the overpressure shock of the blast in that enclosed space could've killed everyone in the room and
the hallway.) It's an insanely reckless thing to do, using explosives to blow open a door that your own son is on the other side of. Manta may love his son, but he's still a bad guy, and that excess aggression in pursuit of his goals and failure to consider the harm his actions can cause are part and parcel of what make him evil.