I think what's being overlooked here is Tupac's loyalty. I don't believe that Tupac had any affiliation with gangs except in regard to the fact that many of his friends at Death Row were members of the Bloods. However, their Blood-affiliation is mostly irrelevant. We have to remember that Tupac was fiercely loyal in almost everything he did. When it came to his fans, songwriting, albums, labels, friends...et cetera. He even went so far as to attack other rappers and celebrities that he felt were being disloyal to their own people. For example, going at Eddie Murphy for not contributing money to help his people - not giving money to the ghetto and relentlessly attacking people he felt had been disloyal to him - Puffy, Biggie - and those that affiliated with them, even to minor extents - Nas, Chino XL, Mob Deep, et cetera. So what I'm saying is that it didn't really matter that many of Tupac's entourage were Bloods, only that they were his friends. Furthermore, as we all know, his ego was very much out of control at this time and it didn't matter to him that Orlando was a well known gangster. Even though he knew in his heart that he wasn't invincible and could be touched, he often didn't let this knowledge influence some of the self-destructive decisions that he made. I think that Tupac would have done the same exact thing had none of his affiliates been gang members. They were his friends and he was deeply loyal to them. To go even further, Tupac had always been somewhat of a loner and the fact that Deathrow provided him with a family-like atmosphere made him see past all the controversy of which he should have been very critical. He also felt somewhat indebted to Death Row for getting him out of prison. Some of this comes out in his lyrics - "Destination Death Row, finally found a home." I also agree that Tupac was very pumped up after the Tyson fight and that definately played an integral role in his decision to go after Orlando. This rush of adrenaline, the comfort in knowing that many of his friends were gang-affiliated and his out of control ego that had been cultivated by the Makaveli persona (created for the Bad Boy beef) to instill fear in those who would oppose him all intertwined to cloud his judgment. It is also interesting to note that after the fight, knowing full well that he had just attacked a well known gangster in public, his main fear was not retaliation from Orlando, (which would seem more troublesome) but the fear of going back to jail for violation his probation.
Anyway, just my thoughts.