My lecture begins...
IMO, the written or spoken use of the "N-word" and "retard" points to
the character of the speaker, not the person or behavior, or the listener.
For parents and relatives of individuals with disabilities, the word "retarded"
is not just some simple, clean, description of some silly/immature action.
It's has become a degrading, prejudiced word that conveys that
the speaker has little or no respect for their child.
... particularly since that same kind of "retarded behavior" can/does
come about through accident or illness, not just mental maturity.
The word used to be in the name of the national organization,
the ARC, Association for Retarded Children. As those children grew older,
the group changed the name to Association for Retarded Citizens.
Now, due to inappropriate schoolyard use of "retard", the organization
has become simply, The ARC of the Untied States.
The Wiki description of "Euphemism treadmill" with respect
to Disability and Handicap is worth reading (
here)
Ironically, parents originally used the word "retarded" as a word of hope !
... their hope that with time their child catch up and eventually be "normal" for their age.
But the degrading use of the word by others prompted the changes in the meaning of the ARC.
If you're not a Black-American or a relative of a person with disabilities,
you are probably not feeling the real pain the use of such words can/does inflict.
My bottom line is in my signature below...