It isn't required that one be active in a community to consider oneself part of that community, or to be angry about something that community does. I see no reason to assume bad faith or doubt their sincerity of motive. Consider that the phenomenon of FLOSS contributors "leaving because of something dysfunctional" isn't simply a trend that people choose to ride on, but a sign of actual political and philosophical conflict within the community.
It rides on the wave of FLOSS contributors leaving because of something dysfunctional, and he was leaving because he wasn’t active, but makes it about something political, since it would get read because of mentioned context.
Had he just posted his opinion and not left, it would not have been noteworthy.