You should make it more personal than simply listing the symptoms if you want anyone to take it seriously. Also, try to think how his friends would react to the information you're intending to provide. Would they think 'socio or not, he's still the same person' or would they be freaked out? Personally, I fail to see your current plan to be successful enough to be worth the time.
Getting back at someone who might be a sociopath is also quite risky. Besides, what would you gain by doing that except stirring his life a bit for a while?