Paula

1 Timothy 1:19-20 
holding on to faith and a good conscience, which some have rejected and so have suffered shipwreck with regard to the faith. Among them are Hymenaeus and Alexander, whom I have handed over to Satan to be taught not to blaspheme.

The interlinear tells me that it is The Faith that these men were ruining, not individual people’s faith. They were turning people away. And I don’t believe Paul would turn unbelievers over to be taught a lesson. So these are believers who are turning others away from The Faith.

I believe your stalkers are in this category. They are turning the lost away and injuring the faith of the weak; they give Christianity a bad name. They need to be taught a lesson!

Or look at the man Paul wrote about in 1 Cor., who was living with his step-mother. He was thrown out and handed over to Satan. Later, in 2 Cor., Paul instructed the people to reinstate the man because he had repented. Surely this man was a believer.