What I think is *actually* harmful for the JS community is this kind of witch hunt.
Maybe Sean was in a bad mood, or perhaps frustrated that MooTools is back from the dead just to bust the new attempt to extend JavaScript's standard library (again!). You can't judge him for just that.
That whole thread gives me a stomach ache, with all those passive aggresiveness. But they're all reasonable people, so I think they will clarify soon.
That being said, Sean Larkinn is *not* webpack. The former is a person, the latter is a great project that's pushing the web development community forward by setting new, remarkable standards of dev tooling. webpack isn't made by just Sean and will survive Sean's contributions.