Why do some Christians threaten some people that they will burn in Hell?

I was reading today about a Christian preacher shouting at two homosexuals that they would burn in Hell. I wonder why anyone would do this. Do they think that what they say will scare 'sinners' into giving up their 'sin'? - Surely they know that that is not at all likely to happen. - Most people these days do not believe in God, and an even larger majority of people do not believe in Hell, or that homosexuals will go to Hell. - And why would a preacher who believes in God want to make unbelievers start to believe in a God who punishes 'sinners' to an eternity in Hell? Do these Christians want non-believers to believe in such a cruel God and to become as hate-filled as they are?

Years ago, crazed with long, unbearable toothache and months of inadequate sleep and insufficient food, because of the long, cruel negligence of senior dental staff at the Charles Clifford Dental Hospital, I became suicidal. It seemed to me that death was the only way to end the pain. A retired vicar who lived near to me at the time wagged his finger at me, and with a face contorted with anger told me that if I killed myself I would go straight to Hell!

I was already in Hell. See here and here.

Why, I wonder, did the retired vicar not direct his remonstrations and threats to the dental staff who were responsible for my continued suffering and who could easily have dealt with the abscesses for me and ended my pain and sleeplessness? - That's an easy question to answer: he didn't have the guts. - He did say to me once that he had written to an important churchman he knew - a Dean of a Cathedral - and asked him if he would help me to get the treatment I was being refused! - This other guy - the Dean - also lacked guts. - He'd written back that he would ask the negligent dentists to deal with the toothache for me if I would first obtain a certificate of sanity that he could show people so that he didn't get into trouble for intervening on my behalf! - The retired vicar then toddled round to me and asked me if I'd let him have a certificate of sanity!