I suffer from aspergers in some form or another(diagnosed by Dr.). While im usually "normally" functioning, I happen to have wierd sense of humor, lack some social skills and being too concise at times. These things crop up usually when around extrovert people(like non-tech people stereotypically are) and it can cause them to feel that I'm intentionally hostile towards them, where as it's more about me(unconsiusly) feeling outside their social wavelength. I don't want to be hostile towards others, but my capabilities for social interaction often cause friction unintentionally, and some people are more sensitive to take offense becouse of it. How people react to my actions are also really varied, biggest factor(be my speculations) being their social backgrounds(groups like family/friends/prev. workplace/school/generation/culture).
Maybe what I'm trying to say that it might not be entirely fault on the sSDE. Maybe the non-tech people haven't had experience working with someone who is less extrovert than their social group before. Too many times i have seen that introvert and socially "handicapped" people are left behind just becouse they are different.
Not every anti-social behavior is malicous or intentional. People react to different interractions differently. People can learn to accept peoples differences and live with them. Working on their work relations is a good start, since sSDE has said that he wants to make it better.
--Sorry about my (personal) ramblings and bad writing(non-english speaker)
Indefensible issues can include:
"I'm jealous."
"He's wicked smart and it makes me feel inadequate."
"He's hot. I would hit that, but I'm married and he's a coworker, so no. Now I need an excuse to hate on him and alienate him."
That last issue is one they should not admit to, you should not poke at, etc. But it also shouldn't be a reason to fire a guy. Reality: A lot of people cannot cope long term with platonically working with someone they find attractive and this is frequently resolved by one of the two changing jobs.
To me it doesn't sound like he is a problem, it's sounds like he has integrity. And that you shall not bend.
I had colleagues from all over the world and found that I generally meshed well with those which matched my attitude of calling a spade a spade, but conflicted with those which took the opposite approach. Even a (IMO) statement such as "I'm not totally on board with this idea yet - could we look into estimating the cost of this feature before we start coding?" would raise hackles.
It is my belief that there might just be some cultural sensitivity training required in OP's scenario.
Did you try to do some team building activities with the whole group? Sometimes getting them to connect on a more personal level gets people to open up.