I thought I addressed why saying "No Jesus No Heaven" isn't calling you a bad person. Anybody who has ever seriously discussed religion has had that conversation. The official stance of Christianity is: many good people won't go to Heaven, because they're not believers. That is their belief. Many religions take the exact same stance: in order to get whatever divine gift they promise, you kind of have to believe in their God and their teachings. It's a package deal.
The flipside to this is that a non-believer isn't necessarily a bad person, even according to Christians. They might be wonderful people, they just don't get into Heaven. So that really kind of undermines the whole "it's a statement of superiority" business. Anyone who takes it as such is making an assumption that the guy thinks you're a bad person.
However, if he had added "neener neener neener" on the end of the sig, that'd definitely tip the scales in your favor.
Oh I understand why people get butthurt over stuff like that. It's because even non-believers like to think that they're going to Heaven, if it exists.
So you agree with him that you're not going to Heaven? What's the problem then?