People start complaining something is a monopoly when the business starts squashing potential competition from the position of power, using bully or shady tactics, or screwing their customers by being more and more greedy.
In case of Microsoft and IE, even if you don't read up on the history and details of it, it's obvious that they were just trying to do what Google is doing now - gatekeep the web and get some of that toll money. I don't think many would have issues with Microsoft just including a simple web browsing tool and leaving it at that. Instead, they were actively working to kill the competition, took over the majority of market share and then just killed off innovation basically completely, and held back the web for years and years afterwards.
In case of Microsoft and IE, even if you don't read up on the history and details of it, it's obvious that they were just trying to do what Google is doing now - gatekeep the web and get some of that toll money. I don't think many would have issues with Microsoft just including a simple web browsing tool and leaving it at that. Instead, they were actively working to kill the competition, took over the majority of market share and then just killed off innovation basically completely, and held back the web for years and years afterwards.