The "one" part is out fault for not using Bing, but isn't "mediating content" between users and websites essentially the premise of a search engine?
The point of breaking up monopolies is not to make a moral statement about the company, but because we've found that monopolies are generally bad for society.
Honestly at this point it doesn't even matter how good Bing is - we've been unconsciously trained to work with Google's algorithm in particular and they just have a de facto monopoly on the mental process a person goes through to formulate a search. Everyone's workflow everywhere will be worse and take more time if they voluntarily stop using Google, that's not what I consider a fair competitive landscape.
Seems like a recipe to have a worse product.
The argument that they're so good at what they do, they've created a monopoly, I think is very fragile.