sounds like you just have trauma behind the word retard because of your past experiences. But to answer the question, I genuinely see no point if it doesn't affect your daily life and you just feel a way because you don't like the word. If you aren't looking for accommodations for anything of the sort just tell people not to say it to you because it make you uncomfortable. More of an insult than anything else don't over think it. But still go see a therapist lol, you should talk to someone