No need for personal attacks.
Generalizing. It's would be the same as me calling you out as being an 34 male Texas Neckbeard MAGA supporter for having the user name "pessimizer".
As an actual insult, assuming and throwing it at someone is an attack. It could be derogatory if what said harshly generalizes a majority or group.
If GP had said the author was probably retarded, would you be so confused then?
I prefer honest truth to polite fiction.
It’s better to attempt to see the world as it is than delude yourself with bullshit.