It's not an abuse of power, it's a simple decision to block particular content he doesn't want on his add-on providing service. He also removed the ability to post music files on his service too a long time ago, though probably not for the same reason, it's a choice he can make. It's his add-on and his service.
With that, you are still free to post these add-ons on this forum's Add-On section. People can still freely distribute this type of add-on throughout Blockland.
Personally, I'd rather not see any of these types of add-ons in this game either.