Accounts with 15 SP cannot do any real harm to you if you have others giving you decent votes. Just ignore them and concentrate on the good people. They are not worth your time. I don't know who operates those accounts, but Steemit could withdraw their delegation if they care. Nothing to do with Steemcleaners as far as I know. If an account does not post you cannot downvote them. Steem offers freedom that can be abused.