There are many cliches in mainstream comic books. For example, any comic book fan knows that when two groups of good guys meet for the first time, or often any other time, there will almost certainly be a fight for the first few pages until they ascertain each others identity.
Some of the other cliches are a bit harder to pick up on, but once you know where to look, they pop up just as certainly. One of these that I realized over time is that almost anytime a street gang or group of thugs is portrayed in a comic book, they will be multiracial. This is most true of comic books from the 1980s, the era when comic books were most likely to try to portray the gritty, "realistic" world of street crime. It is also true of comic books on either side of this decade, however.
While it isn't true, and is also not a very nice thing to say, that most criminals are from a certain race or class, I think it is fair to say that most criminals do tend to associate with people like them. But you wouldn't know it from comic books, where gangs are almost always multiracial. It would be especially rare to find an all-black or all-Hispanic gang. It should also be noticed that gangs are not only usually multiracial, but ridiculously multisubcultural: they often consist of a hip-hop style black thug, a scruffy looking white guy, a white punk rocker with an extravagant mohawk, occasionally a couple of Mafia looking guys in suits and ties, and assorted others. Despite their various subcultures, they all seem to share similar goals: hassling people for money, or sometimes for fun. It is hard to find all these exact stereotypes, because street gangs usually only last for a few introductory panels before Spider-Man or Batman goes on to fight whoever is the real villain that month, but the pattern emerges before too long.
I don't know if making street gangs multiracial was a matter of official policy. The Comics Code Authority, which was still very much in force at the time, forbade negative racial depictions, and having an all black gang mugging people could be seen as such. It is more likely that it was an in-house editorial policy, although I have never heard such a policy referred to. It was probably, on balance, a good thing, although it does always seem slightly forced to me.
What is more confusing to me than the multiracial aspect is the pastiche of street cultures. Almost all of the Marvel and DC editors were residing in New York City, and most of their writers and artists were as well. How then, does their version of what a street thug looks like come out looking like an elderly farmer's wife in Iowa might imagine? Punk rock, as far as I know, was never associated directly with gangs, and yet we have the guy with a leather jacket and mohawk flashing knives every time Daredevil needs to spend a few pages beating someone up. Presumably the artists and writers were familiar with the scene in New York City, and associated with people from these street cultures, and yet they end up designing their cannon fodder thugs to look like people who must have inhabited the same subculture as them.
The complete sociology of the 1980s and comic books will probably only be explained long after anyone can remember them.