can you explain how someone being incorrect about something weakens their position? i assume the position in question is that their should be more trust busting. "there have been these antitrust actions" isn't actually a counter argument to "there should be more antitrust actions", so it doesn't weaken the position, unless i'm not understanding what you mean by that.
you know what my favorite fallacy is? the fallacy fallacy, the mistaken assumption that by showing an argument is invalid you've shown its conclusion is false.
If someone says 'the level of X is 0, and the appropriate level should be higher than it currently is', and if it turns out that the current level of X is higher than the claimed 0, that does indeed raise doubts about their position.
The argument was they feel they are invincible in their [monopolist] position, and that argument is only made stronger by the cases you cited as none of the outcomes really moved the needle in that aspect.
None of these cases destroyed any of the defendants' monopoly status, so while there have been some "actions", there certainly haven't been any effective ones.