I have a great basis for saying ENTJs like to micromanage people--and that's that I've noticed them doing it to myself and others (and many people complaining about it) in lots of different situations.
An ISFP manager would be more likely to try to talk to the underperforming employee in a polite and non-confrontational way and determine if his needs are being met sufficiently. Dominant Fi would most likely lead him to take the personal angle over the organizational one and make an attempt to reach out this person emotionally and non-confrontationally first.
An ENTJ manager is more likely to decide the employee is incompetent and take over the task or delegate it to someone else.
Maybe your Ni tells you that, but you're mistaken if you think a hands-off approach is characteristic of ENTJs. Why do you think other types so commonly perceive you as dominating, controlling and overbearing?
Even if Ni does usually tell you that taking over someone's work (or constantly telling them how to do it) is not the best course of action, some ENTJs (especially when upset the poor performance) will resort to Te+Se and throw sentiments of letting others work autonomously right out the window. Anyone who's ever had a stressed out ENTJ boss is familiar with this scenario.
I think you're hurt by the stereotype that ENTJs are overbearing micromanagers and so you're taking extra care to argue against it. I'm sure it must suck to be a balanced ENTJ who doesn't do kind of stuff and hear the stereotypes, but they have to come from somewhere.
Unfortunately, despite your best perceptions of yourselves, yeah, people do tend to see you that way. Sorry if that's shocking or if micromanaging isn't your intention, but that's frequently how it comes off to others and it's why ENTJs have a reputation for that sort of behavior. The only people arguing with it are ENTJs who are upset about the stereotype--not unlike the INFPs who spend post after post after post insisting that INFPs don't have a tendency to be overly sensitive.
Even if it's not true of you personally, it might very well be true of many people who share your MBTI type.
Dude...just stop embarassing yourself...