I believe that WD40 helps to break down the glue, but its been a while since I've had to remove stickers.
More importantly though, don't remove them with your bare hands. There were posts over on Reddit about a year or two back where far right stickers had been put up with razor blades under them, so that anyone trying to remove them would cut their fingers.
It was Reddit, so there's a decent chance that the post was bullshit, but why risk it?