First, I will say that I support an autistic person’s right to choose if they will be identified with person-first language or identity-first language.
Second, I will say that in multiple polls, an overwhelming majority of autistic people indicate they prefer identity-first language.
Third, I use and support identity-first language for autistic people. But I will never rail against non-autistic people who use person-first, because they may not know why it is a big deal in my mind. Instead, I will venture to educate those people about the difference, and encourage them to use identity-first language unless an autistic person specifically asks them to do otherwise for them.