As an ESTJ, I believe that my disagreeable side comes from J, the judger. I can't help but form an opinion on anything and everything, regardless of its usefulness. The T, thinker, uses the brain to understand the world in great detail. I don't accept face value. S, sensation, means I must experience something. I can accept anything, but I am more comfortable doing it to truly understand it. The E, extroversion, is my fearless, almost naive way to explore.
None of these functions independently. It is the combination that makes the personality maneuver and flow. For the sake of understanding how ASD influences these traits, consider that we still don't understand ASD enough beyond something associated with neurological wiring (simplified version). The why, wherefore, and how is a scientific quest. These personality traits could be exacerbated by ASD, but like anything in autism, it's a question of degrees. I do not feel that ASD makes me agreeable or disagreeable, but I know my personality does. I would need an NT clone of myself to see how much one might influence the other. It's like taking the color purple and separating the red from the blue to measure percentages.
One must consider the dangers of labeling personalities and categorizing people for their faults and virtues. This is commonplace in business career placement strategies, but it shouldn't be thought of as a real science. My personal life has no place at work, and my work has no place at home (easier said than done), so any person can call upon the applicability of their traits for certain tasks and actions. ASD doesn't tell me to be polite nor exclude good manners when called upon. ASD doesn't dictate my ability to be agreeable, but the fact that I am an extrovert and I have opinions as a judger means that I might voice my view more often than not, regardless of it being welcome or even needed. Oops, my socially awkward Asperger moment.
We may be looking more at how disagreeable and agreeable personalities exist without the influence of ASD. I've known NTs who become very disagreeable if they don't get their way, in the manner of a spoiled child. I'm also very impressed by people on this forum who can keep their cool and be very diplomatic in response to outrageous statements.
Since childhood, I have been very obedient. I learned respect for authority, kindness, manners, and I am never late for anything. ASD has nothing to do with these. They were learned. My ESTJ side is woven into my interaction with the world. From the big mix of environment, ASD, and personality traits, we develop our way of functioning. ASD can hinder me in areas, but make me exceptional in others, only because I am keenly aware of what makes me different from the NT world. When I analyze my value, I realize that I have all the ingredients appropriate for someone whose job is to check a jumbo jet before it leaves the ground (just don't tough my tools). Somewhere in the big mix, I am driven to absolute perfection in ensuring completion of the tasks. There is no way for me to know exactly where this all comes from, suffice to say it is the mix.