They made a post about not using 'retard' as an insult. It got caught up in a lot of discussion about whether lack of mental capacity itself is legitimate to use as an insult against people who are not mentally disabled (ie 'moron', 'idiot', etc).
I saw that thread, there were some extremely weird and gross responses, one person wrote like 6 paragraphs on how they couldn't stop using it, with one of the reasons being they "liked the mouth feel"??? It's baffling the lengths people will go to to justify saying a slur.