Marvel sold the movie rights to the X-Men and Fantastic Four. Do people treat Fox with any ill will today?. Don't people wish the rights would go back?. Do people insult and name-call Marvel because they made a mistake?.
It's not really about him making a mistake -- that would be sympathetic. It's saying nonsense like:
"The belief, widely spread by CDPR, that the games made me popular outside of Poland is completely false. I made the games popular. All of my translations in the Westincluding the English onewere published before the first game."
When the guy has access to his own sales data and can see that probably 200 copies of the Witcher books were sold before the first game was released, yeah he's liable to ridicule.