AdNauseam is silently clicking ads. This directly costs Google money. Google happens to control the extension web store for their own browser. Removing it from the store really isn't that bad. Uninstalling it from existing browsers as malware? A little more malicious, but I would still consider it self defense.
There is even a method to install it directly[1] which AFAIK Google has not blocked.
Granted, if Google were not both running the browser and the ad network, these actions probably wouldn't have been taken. But the whole attitude that this is some sort of tyrannical thing is a little over the top.
1. https://github.com/dhowe/AdNauseam/wiki/Install-AdNauseam-on...
This is the exact sort of thing anti-monopoly laws are intended to work against: that a major market force in one market uses that power to intrude or support itself in another market. Since Google Chrome undoubtedly has a sufficiently large market share that this may be a concern and the removal of this extension certainly affects the advertisement market, this seems like a very dangerous move for Google.
Yes, it may be considered “self-defense” but is the cost incurred really so large that they want to risk another lawsuit?