The Vulcan society decreed it best to live without emotion and to suppress them the best they can, and this is where they divide. Since Vulcans tend to show slight emotions and they are usually superficial, can they be considered sociopaths? Most sociopaths are law-biding citizens and have little to no emotions.
Let's look at the definition of "sociopath".
Dictionary.com defines it as
a person with a psychopathic personality whose behavior is antisocial, often criminal, and who lacks a sense of moral responsibility or social conscience.
Does your typical Vulcan fit that? No. Vulcans feel moral responsibilities, though they are arguably not outwardly driven by them.
Oxfard Dictionary defines it as
A person with a personality disorder manifesting itself in extreme antisocial attitudes and behavior and a lack of conscience.
Does your typical Vulcan fit that? No, they have consciences. They know right from wrong.
Psychology Today lists common traits and warning signs of sociopaths including:
- Superficial charm and good intelligence
I don't know that I'd agree with "superficial", but they're intelligent. Push.
- Absence of delusions and other signs of irrational thinking
OK, no irrational thinking here. +1
- Absence of nervousness or neurotic manifestations
The average Vulcan is almost always calm and collected. +1
- Untruthfulness and insincerity
- Lack of remorse and shame
They may lack remorse outwardly, but that doesn't mean that they don't feel it. -1
- Inadequately motivated antisocial behavior
Arguable, as they're not exactly party animals. But they don't typically actively avoid social situations. -1
- Poor judgment and failure to learn by experience
- Pathologic egocentricity and incapacity for love
We know this to be false from Spock's reactions in various episodes and movies. -1
- General poverty in major affective reactions
Arguable as they tend to hide emotions. +1
- Specific loss of insight
What do Vulcans do if not analyze and find insight? -1
- Unresponsiveness in general interpersonal relations
Again with not being overtly friendly. -1
- Fantastic and uninviting behavior with alcohol and sometimes without
- Suicide threats rarely carried out
- Sex life impersonal, trivial, and poorly integrated
Arguable, but we do know that Vulcans feel love. We may allow that many, even most Vulcans view it more clinically. +1
- Failure to follow any life plan
So, after all that, do Vulcans fit the definition of a sociopath? Comparing against the Psychology Today warning signs, we have 4 positive warning signs, 1 neutral, and 12 negatives.
No, one can not reasonably conclude that Vulcans are sociopaths.