My take on people reclaiming the r slur, as someone with cognitive and developmental disabilities. Warning, I will be referring to a racial slur in this post. It will be censored.
The r slur means slow. It is made specifically to mock "slow" people like me, people with a specific group of disabilities that impair us in a very specific way. Unless you are someone who is slow, that word does not apply to you and your cannot reclaim it. Honestly, even I hesitate to say it because while I have one of those specific disabilities, I am not intellectually disabled and so my ability to use that slur, to me, is not promised and I do not want to offend.
"Who are you to tell me I can't reclaim a slur used on me?"
Okay, so here's the thing. I'm Irish. Back in the day, racists used to call the Irish white n-words. That slur has been used against the Irish just as the r slur has been used against you. For the Irish, people hurled the meanest thing they could think of at us, and to them, comparing us to Black people was the worst thing they could possibly do. Similarly, ableists have referred to you as the r slur because they think that comparing you to people with intellectual disability is the worst possible insult they can hurl in your direction. Are you following?
Do the Irish have the right to reclaim the n-word just because it was used against us to "insult" us by comparing us to Black people? No, of course not. Because even though that word was used against us, it's a slur against Black people. Irish people who aren't Black don't get to reclaim that slur. Only Black people can reclaim it.
Similarly, if a straight man who was just a bit too queer-looking is bullied and called the f slur, because comparing him to gay people is the worst insult his bullies can think of, does he have the right to reclaim the f slur? No. The slur doesn't apply to him. It's been hurled in his direction but at the end of the day, he isn't gay. Just like the Irish aren't Black, and you are not intellectually disabled.
The r slur was made specifically to target people with intellectual disability. Outside of people with intellectual disability, there are very few groups to whom that word applies.
You can't reclaim a slur that doesn't apply to you. Even if it was used against you, there's a difference between being insulted by being compared to someone like me and actually having that word hurled at you because you are like me. I'm sorry people were ableist to you, but that's not your slur to reclaim. There are ones that apply to you. Ableists were very thorough. Please reclaim one that applies to you.