I was recently approached by a Jehovah Witness trying to foist some of their cult material on me. I usually just politely decline but this time I quoted John 1:1 and John 1:14 in support of the Trinity(which they deny). She literally went crazy...started getting in my face and yelling about “Christians like me” turning people off. I guess God is serious about His Word being an offensive weapon that does not return void.
He's also serious about not casting (your) pearls before swine or giving that which is holy to the dogs. The very nature of a cult has at its core brainwashing.
I preached full-time for around 25 years and never had any luck with any of the four major cults. One study I had with two Mormon "missionaries" had one of them asking some very interested questions. Our time ended and when I showed up for the next study, I learned they had transferred him back to their re-education center.