Right? If I saw a screenshot from Elon saying "I believe the solution to world hunger is to grind orphans and poor people into sausages," I'd have to check if it were true because dude is unhinged.
the real one isn't better tbh (tl;dr: he originally tweeted that 'cis' and 'cisgender' are slurs, also many links are down because of his whole rate limit policy)
Literally any words could be made a slur dependent on how you use them. It's the ones that are near universally a slur, such as the N word, that anyone should care about.
The fact he didn't feel the need to censor cisgender would be enough to tell you on what level that "slur" actually is.