Once again, we use common sense. Is hell literally a fire? I don't know. Maybe. Maybe not. But it doesn't matter. The point is hell is a miserable place, maybe unfathomable to us so simply described as a fire, a somewhat imaginable torture to us. The message is do right and be rewarded, do wrong and be punished. This is an easy choice, not a "selfish" one. You should want to do right over wrong anyway, so the choice should be extremely easy.
If I call your arguments do I literally mean your argument has gained a bunch of unhealthy weight and become ill with some disease?
So again, I ask, how do you ever know when to take anything literally or not?
If you don't know if hell is a place of fire, then what are we talking about when you say "common sense". If a lake of fire is anything other than literal fire, then common sense breaks down, doesn't it?
Personally, I don't see how "non-believers will burn in a lake of fire" and "an argument is flabby and sick" are similar at all. One is clearly just an expression, and one might actually be a place that exists in reality .... like you said, we don't know. So what is "common sense" when we're talking about shyt we have no proof of? I think this is the point you're missing.