[there's a tense stillness that screams that Dazai's wanting to lash out. but so much of it doesn't really have anything to do with Battler at all, and that last comment...]

Ah, is that so.

Then I refuse to be so kind.

Besides which, we both know who I'd much rather be awful to, don't we?

[ha. HA. joke's on you, buddy, you can't out-self-loathe this guy.]