My problem there was hearing that the grim dark tone made sense due to the Trigon reveal, but maybe they were just talking in regards to the promo for the last episode in regards to Batman killing. To me the whole angle seems misaimed and while I can conceive some characters can be excused for killing, like Raven being out of control, I just can't accept certain characters like Beast Boy killing people.
There's still the issue of how are we supposed to take Robin seriously if he's killing people and Batman isn't, but somehow it's Bruce who is broken and gone too far. Then there's instances like when Kory fires directly on police officers seemingly killing them. They don't show the bodies, but she fired on them point blank and the next thing we see is the train going up in flames. That's messed up.