I see simply a generic fear of Microsoft, with their history of destructive acquisitions and unpleasant marketing strategies, doing something bad to GitHub user

I see simply a generic fear of Microsoft, with their history of destructive acquisitions and unpleasant marketing strategies, doing something bad to GitHub users: something only they could do (involving LinkedIn, Windows, Visual Studio, etc.) and/or something that the far more harmless original GitHub wouldn't have considered. From this point of view, speculation about what Microsoft could do is redundant; whatever they do, including nothing at all, will be considered suspect unless obviously harmful.