system
Given the following post, respond as if you're commenting on Reddit:
human
CMV: Stereotyping is often logical and a perfectly normal application of human reasoning

Stereotypes are perpetuated because there is some truth to them. Bad or absolutely false stereotypes are rarely common, because failure is like natural selection. People use stereotypes as a short cut to knowledge, because we almost never have all the facts to make an informed choice. So people fill in the gaps, sometimes that will prove to be incorrect, but if it is more often correct than incorrect it is providing potentially valuable data. 

Example, if you are walking down a dark alley and some guys are following you, there are a wide variety of valid stereotypes to approximate how much danger you may be in. It is not required for them to be always right to be useful.  A guy covered in tattoos may be completely safe, but is he as safe as someone without any?  No, of course not.  And if you think so, you're simply misinformed or willfully ignorant due to social avoidability bias.  If they're a bunch of young black guys, same thing, it's just more socially unacceptable to think such a thing.  Are they women laughing together?  No reasonable danger.

So people and society should not be made to feel bad about applying simple logic.  Until crime metrics change, stereotyping is here to stay.  There is no way to effectively eliminate it without solving why the stereotype is applied.  I understand it is demeaning and insulting to be stereotyped, but your feelings don't really change the facts.  In the case of covering your body in tattoos, it was actually a choice you made, which removes all moral authority to be offended in the least.

Studies have been done which indicate that there is a positive correlation between intelligence and stereotyping, however intelligent people are quicker at reversing a stereotype that they find unhelpful or invalid.
gpt
There is a subtle semantic distinction here that may explain the issue.

Most of the things you mention are not stereotypes.  Most of you the things you mention are *expectations* about certain groups.  A stereotype is an *expression* of an expectation about a group, not the expectation itself. Acting on these expectations by treating people of different groups differently would be called *profiling*.

So for instance, by your example: a guy with tattoos mugging you would be falling into a stereotype about guys with tattoos, and someone writing a character of a mugger with tattoos into a book or TV show would be *stereotyping* people with tattoos.  Being scared of being alone in an alleyway with someone with tattoos would just be an expectation you have about that group, and acting on that expectation by staying away would be profiling.

In general, we are against *stereotyping* (as in, creating representations of groups that fall heavily into the stereotypes about that group) because it tends to lead to the stereotypes being over-represented and giving people inaccurate probability assessment.  For instance, yes, the average person with tattoos may be more likely to be a mugger than the average person without tattoos; however, the *vast, vast majority* of people with tattoos are not muggers, yet stereotyping may cause 80% of media representations of fictional people with tattoos to be written as muggers, giving people inaccurate expectations about their relative peril.  The same s true for stereotypes about minorities, women, men, white people, poor people, rich people, etc.

To the extent that your *expectations* are actually accurate, there's nothing wrong with holding them and using them to inform your actions.  However, the reason many people are against *profiling* is because very many of the expectations people hold are provably inaccurate due to stereotyping in the media causing them to overestimate the prevalence of the stereotyped traits. 

So, basically:  most of what you speak in favor of is either expectations or profiling. In theory there *is* nothing wrong with those things if you do them accurately, but most people do them inaccurately *because* of widespread stereotyping.  Widespread stereotyping is bad*because* it gives people inaccurate expectations which leads to improper use of profiling, thus screwing up the entire system.