If all Poettering did was community outreach, you would have a much stronger case that he's bad in all aspects of his job and should be fired. Trying to pressure Red Hat by saying it 'reflects poorly on you' is basically saying 'you should get rid of this guy even if you think the good outweighs the bad, because I don't like him.'
If this is true, then this is exactly _why_ the criticism should be directed towards Redhat. Because in his arrogant world view, he can do no wrong, so he will not report to his bosses that he has ineffective community leadership/stewardship. The only way his bosses will know of his ineffective leadership/stewardship is if the criticism is directed towards Redhet, and therefore, his bosses.
I.e., the criticism has to go around the roadblock, Poettering being that roadblock.
Three employees among thousands, representing two projects out of hundreds. Why generalize from that sample? Why ignore all those contributions to the Linux kernel or Fedora, OpenStack or Kubernetes, gcc or coreutils? Some pretty good leaders in there. And if "creating leaders" is supposed to be how we judge companies, what should we make of much larger companies where few employees engage with the community at all? I don't even mean unpopular companies like Microsoft or Oracle. What about Google, for example, or Apple? When it comes to community leadership, they're net negatives; existing leaders go in, and are never heard from again. When every single developer at a billion-dollar-a-year software company is engaged with some open-source community or other (often several), there will be a few losers. That's a poor reason to insult thousands of others.
The whole thing reminds me of how priests and monks would debate the number of angles that could dance on the head of a pin.
Poettering, being a high profile employee of Red Hat, is one of the faces of the company. Because of this, I would argue that Red Hat has a duty to step in from time to time to tell him that what he is doing is harmful in the long term. If they don't do it soon, I can almost guarantee there will be a lot fewer support contracts for Red Hat in the months and years to come; they just don't create dependable developers.