Does he say it to white people?
You do not need to explain tourettes, I understand tourrettes. It's almost patronizing to assume this is a conversation about not understanding what a disability is.
This is a conversation on mitigating harm, and you can cause harm and slurs cause harm even if you're disabled and it's unintentional. Asking for some kind of apology or accountability is the least that can be done.
Brushing this off surprised we (Black people) are offended is shallow bullshit.