You've got the contrapositive there. The claim was that folks who love Rust do not accept criticism of the language. Therefore, a criticism by someone who loves the language was presented, to show that claim was false. Your parent isn't saying that only folks who love Rust can criticize Rust.
Point A: The claim was that folks who love Rust do not accept criticism of the language.
Point B: a criticism by someone who loves the language was presented, to show that claim was false.
Point B does not contradict point A at all. That is like saying that is false I cannot accept criticism because , hey, look at the weak points I have and I gladly mention("I am too perfectionist","I work too hard", "I put the wellness of the company ahead of myself")
