It's sad that Steemit's account verification failed so badly to allow this sort of thing to happen in the first place. There are ways to get their delegation removed from accounts to reduce their voting power and I hope that can be used on these. Then their lack of resource credits should reduce how often they can vote. This sort of abuse is very bad for the platform and Steemit should do all they can to deal with it.
RE: How Steemit is infiltrated by abusive account networks