I know I'm behind, but I just found the podcast not too long ago and am working my way through them. In the discussion of See No Evil it's brought up that Batman really does a number on Lloyd. Well, in The Underdwellers Batman says something to the Sewer King about not being the judge and jury, but wishing he was that one time. Both episodes involved children somehow, and if you think about the child molester undertones in See No Evil, the beating he gave Lloyd makes even more sense.
Also, perhaps Batman let Kimmy run off by herself because he knew he was gonna beat her dad, and even though he was a slimeball he didn't want to make her go through what he did when he watched his own parents get murdered.
The end of the episode kind of helps that theory along as well since he checks up to make sure the girl is ok later.
Just my thoughts.