There's schadenfreude to be had both about the Left demanding body cams and about the police unions' vociferous opposition to body cams, both for the same reason: more often than not body cam footage vindicates the cops.
Of course, the presence of body cams also makes the behavior of truly bad cops (like using drop guns to falsely incriminate a shooting victim) harder to pull off -- but that won't show up in footage, either because the presence of the body cam dissuaded the bad cop from engaging in bad behavior, or because the bad cop had to be more careful (e.g. planting the gun so the act doesn't show up on camera).