As an open source developer myself, I don't understand how it's possible. Why would you give away your labor for free if you don't feel empathy towards others?
My general level of empathy for people I don't know has declined significantly over the past decade and my open source contributions have also declined in line with that. I just don't see the point anymore.
I met some very good people through open source but, overall, the experience has taught me that most people on earth range from neutral to horrible.
Open source probably represents the best kind of environment to meet the best of humanity. The smartest of the good people... But it's still disappointing.