In the cartoon world the beams stop as soon as it hits someone
They should have curved and kept following him instead of hitting the parademon.
They curve but not instantly. If you time it at the exact moment you can cause them to hit an unintended target. For example, Darkseid shoots Superman once and Wonder Woman blocks it with her bracers even though they'd normally go around her and hit Superman anyway.
Shouldn't they be traveling fast enough to have hit Batman before that moment anyway? I mean here:
It looked like super speed was needed to outrun them.
for the purposes of creating a cool looking animation / scene, the beams travel much slower in cartoons than the comics show them to travel. the reverse will also happen, in both comics and animations where superman doesn't dodge things he is clearly able to dodge.
I can understand if they make changes for visual purposes, but it just seems a bit farfetched that Batman can avoid being hit under these circumstances. ---