These stereotypes don't even actually exist outside of the internet. Nobody calls my INFP friend emo, or my ESFP friend a hedonist IRL.
Um no, the internet has nothing to do with it. Those stereotypes exist among anyone who knows about typology and discusses it regularly with others. There's no reason this has to occur on the internet.
Most books on the topic (if you've even read any) will explain both the positive and negative sides of each type, which will show you where the stereotypes come from.
It's only when you analyze these things online that you start to create these stereotypes. When you don't understand a person's thought processes (when they're especially different from your own) you likely wont even notice they are occurring.
I don't even remotely understand your insistence that stereotyping people based on behavioral trends can only occur on the internet. That's really out of left field.
Personality stereotypes occur all the time and exist in people's minds even if they don't know typology terms. Typology is really just more sophisticated name-calling. Everyone knows what it means when you say "That guy is a jerk" or "She's such a brainiac" or "He's really got his head in the clouds!"
We all stereotype each other based on past experiences of behavioral trends all the time, and from these experiences we build archetypes to describe rough representations of arbitrarily defined groups of personalities.
And in this particular classification system, the ENTJ archetype is
defined as the in-charge executive type, which frequently (though
not always) results in a tendency to micromanage. That's in the definition of Te, which you'd know if you'd bothered to read any of the literature on the topic of typology.
Instead, because you're pissed that a characteristic you don't like is typical of your archetype, you've pulled the nonsensical idea that Si is "required for micromanagement" completely out of your ass and continued to harp on "BUT OMG Ni DOESN'T LIKE DETAILS!!!!" for post after post while completely missing the point that the micromanaging tendency is far more related to Te/Fe than it is to any introverted perception faculty.
I mean, think about it. What
is micromanaging? If you think about it for a minute it's just intuitively ridiculous to imply that any external organization process could be rooted more in
introverted perception (which deals with interpreting personal meaning) than in
extroverted judgment, which deals with--you guessed it--organizing the external world.
Now, when you take Te's natural micromanaging tendencies and combine them with Si's preference for sticking to what it already knows, you get a
worse case of micromanaging than you do when you combine it with Ni's preference for seeing numerous different angles...
...but this doesn't change the central point that the act of organizing the external environment is inherently associated with a Te/Fe attitude in the first place, not Si/Ni.