On the contrary, I think he handled it perfectly.
I've become exhausted with most discussions on social media, because conversations frequently get hijacked by loud people with strong opinions that don't express them in good faith. Without strict moderation, it can become impossible to have a rational discussion on certain topics. For example, pretty much anything on HN involving Google devolves into worthless noise.
In the case discussed in the OP, Poettering clearly has no intention of changing the default configuration (at least based on the reasons given in the issue), and has provided a way of modifying the configuration for those that care enough to change it. There's no value in further debate, and closing the issue to further discussion keeps Poettering and other contributors from getting distracted/burned out by unproductive conversation.
If people don't like it, they're free to fork Systemd or start up their own competing software project, and then they can handle community interaction for their own project in whatever way suits them.
Frankly, I wish more discussion were handled this efficiently.