Perhaps the rule could be that paladins may not associate with people with two or more stats of less than 2. Something like 0-2-2-2-2, he can associate with - and that would seem, in fact, to be a ordinary selfishly neutral character. And a paladin can associate with those, if only to show them the better way.

More importantly, it seems trivial for a Lawful Evil character to have 11 points total (and thus pal around with paladins) even with Fairness 0 and Care 0. The traditional description of devils/baatezu makes them sound extremely concerned with Purity. As I mentioned at Amp’s, they spend centuries working their way through the ranks before purifying themselves in the Pit of Flame to become pit fiends. Even worse, those sources say that bone devils act as cultural police who can send even higher-ranking devils (except pit fiends) to the Pit (without promoting them). Now, other devils don’t like these police much, but if they catch a colleague attacking a bone devil they will have no problem demoting that colleague to marked lemure with no chance of return. This fits what we know about Lawful Evil types in our own world (see here, Chapter 1, the Posse section.) It also provides a D&D/Planescape justification for Hell’s existence. (Remember that belief creates reality here.) Your ideal Chaotic Evil type believes in the Abyss because he believes in struggle and wants to fight others like himself. He expects to win power through force of arms, but he’ll accept a second death if he can die cursing goodness and perhaps merge with ‘the spirit of resistance’ (to quote a literary communo-anarchist atheist Satanist). Neutral Evil is a whole nother story; we might briefly say that humans in this group believe money rules everything, and an older race exploits this. But Lawful Evil types believe in punishment even when it hurts people like them.