Wow. You're going to double down on using the term. Surprising.
As you may be able to tell from my handle, I'm a physician. Medical school professor with computer hobbies, which is why I'm here.
In answer to your explanation, I think most people would agree that calling people out on contemptible behavior is certainly fine. What isn't fine, is using pejorative terms to do so, as you are then doing exactly the same thing as that which you are criticising. The term for that, since you seem to want to be pedantic, is 'hypocrisy'.
With regard to the term 'retarded', the DSM 5 replaced the term 'mental retardation' with 'intellectual disability' in 2013, the WHO did the same in 2016, the Federal Register removed the term from all US state and federal documents in 2017 via legislation called 'Rosa's Law' (Public Law 111-256), and in 2019 at the General Assembly, the AMA passed Resolution 024 A19 affirming the the term has been struck from currently acceptable medical terminology. It's not used by professionals generally anymore.
Please remember, it's very easy to allow our emotions to lead us into verbal excesses, even when we only have the best intentions. I suspect you understand that, but were piqued at the time.
Thank you for the discussion, and have a wonderful evening.