Reddit didn't ban pewdiepie subs because of the shooting. Pewdiepiesubmissions went private by the mods choice and pewdiepie_submissions was owned by a troll who was posting memes about the shootings and trying to make pewdiepie look bad.

Just FYI pewdiepie_submissions was a fake sub made by someone who seemed to have mental problems and was spamming memes and support for the shooting. He made dozens of other fake subs and obsessively harassed h3h3. Pewdiepiesubmissions was made private on purpose by the mods to avoid drama related to the shooting, the admins didn't do it.