that's exactly the point of that thread, there's no need for a reason in everything, sometimes people are silly and enjoy being silly just for the snake of being silly
80% of 4chan is shitposts with no hidden meaning.
The remaining 10% is people dog-whistling to each other through shit-posts, hoping one will slide into the 80% undetected.
And 10% horrible things that the janitors have to clean up.
No offense but if you think there's any kind of subtlety on 4chan I dare you to browse /b for two minutes. No dogwhistles, just regular, very racist and antisemitic whistles.
/b/? We're not in 2003 anymore, amigo. /b/ is mainly tranny porn now. There's no more raids and such. We 4channers got old and now simply drink our beers and laugh at the world. 4chan is and always have been chaotic neutral. The weapons boards /k/ for example is very pro Gun rights but also very pro Ukraine. They cheered Hamas but now shit on Houthis. /pol/ is actually reddit refugees and Indians. All other boards treat /pol/ with disdain, except /tv/ which is also full of election tourists. /int/ is bizarro /pol/ which hates right wing America but also Indians and Polacks. There is no rhyme nor reason to 4chan. It simply is.
I did as you suggested and I saw people singing slurs around like it's nothing almost immediately. I suppose perhaps given that you have used one in your comment I shouldn't be surprised that it passes you by, but that is exactly the kind of overt racism/sexism/homophobia/transphobia that, I assume, the previous comment was talking about.