From my understanding that was due to a long-running design philosophy clash between the systemd people thinking Docker should be using systemd primitives to manage things like unit startup/shutdown/etc., and the docker people wanting to use their in-house implementations so as not to depend on systemd (and thus rejecting PRs trying to change docker behavior to use systemd). I don't think it's fair to use that as an example of toxic behavior on either side, they each had their motivations, and a consensus needed to be reached for both projects to proceed. From what I can tell that debate seems to be old news these days and I haven't seen as much clashing between those teams. I am not a developer on either side though, this is just from the perspective of a user who follows the Github issues.