In a way the group homeschool can be thought of like a small private school, it's just simpler to handle personal problems in a small group.
Or they can approve of the bullying. Or they can do nothing because they don’t care, or because they’re socially subservient to the bully’s parents.
It’s simpler to handle personal problems in a small group, it’s also easier for them to fester in a closed group.
The parents also have the option of reorganizing the group to kick the bully’s parents out, along with the bully.
This model isn't new and had problems before.
Such involved parents could never let anything happen arguments ignore how these things develop as less involved parents cargo cult. (You can't get much more blatant in a drop in actual involvement than the example in the article.)
These kinds of groups connecting themselves to actual home schooling will erode it by association.
2. If the parents care enough to homeschool, why would they not care about bullying?
3. Socially subservient to the bully's parents? This feels like a hopelessly contrived and niche edge case that is effectively meaningless because it would be so rare
4. I'm not convinced personal problems fester moreso in a closed group (see: armed forces), and further I'm not convinced homeschooling groups are closed in the first place
All this to say I don't think your argument has any merit and is based on convenient and unlikely hypotheticals.