I think their point was less about exploitation but more about the "inflexibility" of autism and how it can impede people from having a positive outcome in a situation. I think their point has been misinterpreted.

This short comic didn't go into detail on what the "bad cause" was. There could be hugely different outcomes from this study depending on the severity of the bad cause. For instance, if the bad cause was being paid to go steal a chocolate bar from a store, there would be dramatically different willingness from both sides than if it were, say, being paid to kill somebody, regardless of the monetary reward. That was not taken into account.

I agree that the fixation on moral values can definitely be seen as a good thing, but there's also some nuance to this because that fixation/"inflexibility" can extend away from good vs. bad causes (morality) and into other areas of life as well.

In any case, I agree that they shouldn't have framed their conclusions that way and it was clearly an attempt to frame autistic people as "inflexible". If they really wanted to prove that point they shouldn't have based their study on moral values.