i am going to disagree.
dexter consistently demonstrates an understanding of the thoughts and intentions of others. he may be acting at times due his differences emotionally, but he can call other people's bluffs and easily engineer his own. He spends all his time studying a person's general routine and sometimes has to predict their intent on the fly or based on their cues. he has the capacity to outsmart people by reading their total package of cues and words, and is rarely outwitted, though the trend has been against him recently due to lack of focus...
if anything, his childhood trauma may be partially to blame for his emotionlessness, as this is a known component of clinical cases of PTSD. However, his obsession and code of ethics is the only aspect that is in common with spectrum disorder (in that it is unusually intense and methodical and he needs to do it). He's simply taken to obsessive levels of interest in his personal ethics. If you study serial killers, you will find that this is a distinct category of killer who feels they are doing a service to society and carrying out ethical behavior. That's why it's such a great premise for the story, as he's the hero in this role.