Is there a term to describe someone that doesn't seem able to differentiate between two words such as "racial" or "racist"? I mean beyond simply overlooking it. Like, you could try to explain the difference but then they just get mad at you. I was thinking stubborn and ignorant, but I feel like there's a more accurate term.
I think it is semantic confusion:
Misperceiving or misremembering a word as one that has a similar meaning, as when lamp is perceived or recalled as light.
And it can result in malapropism:
A malapropism (also called a Dogberryism) is the use of an incorrect word in place of a word with a similar sound, resulting in a nonsensical, often humorous utterance.
In general, the person is wrong-headed:
stubborn in adherence to wrong opinion or principles
Stubbornly refusing to change one’s opinion or chosen course of action, despite attempts to persuade one to do so