At least one reason..

The Eight of Spades Gomorrah card...don't remember exactly which one. 8 of something Gomorrah
I fixed him and loaded him down and went into the Casino...Instant hostility.
Reloaded..took him in with nothing in inventory....transferred things one at a time...got to a card and boom..instant open fire !
So I'm thinking that him having it inventory ( and maybe other cards triggers it )
I transferred cards back and forth with him...went inside and nothing happened.
Only when he has it in inventory do they shoot at him.

I win a prize !!!

I'm pretty sure it is something else, cause I never traded any cards to him.