"Bump stock" kits allow legal semi-automatic rifles to perform similarly to fully automatic machine guns that are tightly regulated by present law.

They enable psychopaths to commit mass murder at scales never before seen, threatening the general public and law enforcement.

Their use in connection with the Las Vegas mass murder shows that they are a public hazard and the manufacurers/distributors are willfully flouting the spirit of Federal Law controlling ownership of fully automatic weapons. 

"Bump stocks" and all similar devices should be banned, or regulated along with machine guns, and all sales and transfers of these dangerous devices should be banned or tightly regulated.