You seem to be oblivious to teenagers using racism, or really anything that is considered offensive, for the sake of being edgy, whether they share those opinions or merely don't care either way.
This is quite evident in 4chan culture. For example "nigger" is used anywhere from positive ("my nigger", "nigger earned his bike") to a catch-all insult ("fuck off nigger"). Similarly the suffix -fag (from faggot) is used in the same way -person could be used. newfag is an insult to throw at people who stick out from the crowd due to lack of subcultural knowledge while drawfag is a neutral to positive term describing anonymous artists creating original content with their skills.
Whenever business and banking is the topic then the involved people will be called jews, regardless of whether they're actually of jewish descent.
"two nukes were not enough" will even be used on boards that actively consume japanese culture to express a very low opinion of something particular.
I don't get why people get so worked up about racist and sexist insults specifically. They are just easy to use because they target large groups. Simply calling people retarded is a classic, but yet far fewer people bat an eye over it using disabled people as a negative. Country stereotypes are also a thing. Anyone with brown skin or near-eastern clothing will be called a mudslime (muslim). Why? Because the group is large. Nobody is going to use satanist as an insult, simply because the group of satanists is tiny and nobody will care to get worked up to defend them.
I'm not saying there are zero racists among the audience. It's just that there is a non-zero and potentially large fraction of what you're perceiving as racism is actually just people spamming things for shits and giggles. In other words, it's immature. It's easy because it offends many people.
To adapt hanlon's razor: Never attribute to hatred that which is adequately explained by indifference and edginess.