I don't know what they all believe. There's millions of them. Don't really care, TBH. They don't cause me any trouble, and lots of Christians I know are perfectly nice people, whatever ideas might be in their heads.
I do know that in general, when discussing these issues with non-believers, they don't tend to take the "Well you're going to hell and I'm not; just you wait till Christ Jesus returns IN TRIUMPH [incidentally, it's always a sign when they say Christ Jesus instead of Jesus Christ — I wonder why] and that'll show you, you'll be wetting your pants and begging for His forgiveness, can't wait to see you dragged off to Hell pleading and grovelling while I'm sitting pretty in Heaven, so yah-boo-sucks to you" approach (whether blatant or veiled). I would guess maybe it's generally seen as a little uncouth to bring up someone's impending torture if they refuse to agree with you, purely as a cheap'n'easy debating ploy (besides being ineffectual, since those of us who don't believe in God or Hell aren't likely to change our minds through fear of it).
Presumably, most have enough empathy that they don't enjoy thinking about unbelievers going to hell anyway. Whereas I've come across a fair few Christians from outside the UK (okay, they tend to be from the US — though there's plenty of perfectly nice, normal Christians there, too, of course) who seem to have no such qualms about vocally celebrating the imminent torture of billions of their fellow human beings on the say-so of their best buddy Jesus.
Mainly, though, I mentioned it because of the dog-walk. The timing of that was what made me wonder if OP was from another part of the world to the majority of MN posters. Despite various posts, it is a UK-based site with mainly UK-based posters, so while anyone from anywhere can read and post, most posts and most threads will tend to broadly reflect British cultural norms. The poster I was responding to was approaching the topic in a way that I haven't seen much from British Christians when discussing these issues, and things seemed to potentially slot into place a little better when there was an indication that they may have been operating from a different set of norms.