You asked me if I "agreed" with that statement. Kinda hard to tell whether you wanted me to say whether I thought it was true and/or right.
Yes, it has everything to do with personal motivations, never said anything else : that's why we judge people, to see whether they could benefit or harm us (to oversimplify), and the only quick way is to make an assumption based on appearance.
In the example, as you yourself clearly state, the "laziness" motivation, or the "getting some" motivation, kick in respectively if what the driver sees is a man, or a woman : he makes the assumption based on that that one is of no benefit, the other is.
To clarify, I agree with the general idea of the op that your appearance should influence the NPCs reaction. Not with the particulars of "Low disposition to the poor, high to the wealthy, high to those who look strong, and low to the weak" - doesn't make much sense to me - nor do I suggest that this reaction should be automatically something as strong as hatred/attack on sight. I'm just working with the idea that the each faction or social class will be nicer with someone they think as their own ; that the guard don't like obvious criminals ; that common folks might get tired, mistrustful and tight lipped at those civil war warriors.