Even if it were though, it seems obvious being on the receiving of that slur would have significantly less impact on you, as it didn't actually target anything you saw as part of your identity. I don't see how your experience puts you in a position to absolve others for their use of the term.
Personally, I think we should give significantly more weight to folks who are actually in the impacted community (those with intellectual disabilities, their loved ones, etc). The vast majority of whom _do_ object to the use of the word as a derogatory slur.
There is no reason for school or experts to retract that claim, because they never made it. The claim was done by other kids.
The parent comment already covered this. You don't believe you are, based on how you've talked about this experience. At no point do you say you identify with the word, just that it was used against you.
> If we trust the experts on this I'm severely handicapped.
I mean they themselves basically said they do not identify with it:
> If people ran around calling you the N word on a daily basis would it be a comfort to you that you aren't actually black?
Anemic, impotent, bald, and on and on.
Language is abstract. Some conditions are generally disfavored. Referencing that disfavor abstractly can be meaningful.
Come now. At the root of all of this is an ableist, patronizing assumption: People with mental disabilities must have the language used around them carefully policed because they can't handle the implied disfavor and emotional harm that language may communicate via their own agency, not like the rest of us.
Your anger at Stripe is reasonable, why are you belittling an entirely unrelated set of people in your attempt to express that anger?