If I thought there was no way to insult someone without invoking a term that refers to a historically marginalized group i simply wouldn't insult people.

You just did though, the dip in dipshit means something like "insane, stupid person", you could say it's antiquated and not used that way anymore, but I think many people would argue the same for words like idiot, or even more contested ones.

...and anyway, if, as the post says, "jobless behavior" is ableist because it implies being jobless is bad, and disabled people have a hard time getting jobs, wouldn't using "uneducated" as a pejorative as you just did be ableist too, since disabled people have a harder time getting educated?

Seriously, think about it, I don't think there is a way to be insulting without using a slur (by the post's definition of one), you certainly haven't given a good example, at least.