God has promised that He will bless those who bless Christian believers and He will curse those who curse them. It will suck to be those persecutors if they don't repent before God catches up with them. The Scripture says that those who fall on Christ will be broken, but those whom Christ falls upon will be ground to powder. I'd rather fall on Christ for grace and mercy than to have Christ fall on me because I haven't repented of my sinful ways.
It is a fact of history that those who persecuted Christians in any century, and who did not repent, died very horrible deaths.