Personally, i don't think there's anything wrong with holding a monopoly as long as it stems from merit.
However, we are proven time after time that power corrupts. Unless there's a regulatory body to watch their every move it seems they'll abuse their dominance to maximize profits.
Even if a monopoly were achieved on merit (I don't necessarily agree that it was in this case), the incentive to maintain that merit disappears once the power is obtained. Even if that weren't true (i.e. if power didn't corrupt) they could simply degrade naturally while the bar for entry would remain too high due to economies of scale and other reasons. And don't forget the incentives against downsizing: layoffs hurt labor, reduced consumption hurts suppliers while withdrawal of products and services hurts customers and the brand simultaneously. People have made better arguments than I have but my point is even a moments thought should make you reconsider your position.
However, we are proven time after time that power corrupts. Unless there's a regulatory body to watch their every move it seems they'll abuse their dominance to maximize profits.