This is one of the quotes on that video which describes it perfectly:
"The point is that this a meeting of the minds. The two recognize each others warrior spirit. If their respective bosses were to order it they would probably kill each other without blinking an eye yet each of the two respectively has the highest possible regard for the other because their lives and values are so similar. With that in mind what more can be done? A quick nod of respect and their ways part again."
The hood mentality is a lot like this. Gang members respect each other because they understand that both parties have values. Only when those values are disrespect/attacked, they will go to war. It is very unlikely to see gang members in conflict on the street if it is just a casual meeting like seen above. If both gangs share similar values and have a common goal/motive, they will work together to achieve this and then disperse after the goal is reached.