It is, if you are leveraging one monopoly to attempt to gain more. This is what happened with Microsoft and Internet Explorer (via the Windows monopoly)[1]

1: https://en.wikipedia.org/wiki/United_States_v._Microsoft_Cor....

Had Microsoft merely provided advertised IE with Windows there never would have been a suit. Even bundling alone would have been a hard case to make. They did far more than just ship IE with Windows.

Oh I agree. I merely meant that they were leveraging an existing monopoly to try to create another one via unfair practices.

linking to my answer in other parts of this thread, since the point and my reply are the same:

https://news.ycombinator.com/item?id=41166997