If the guy was talking to his kid like that, I’m going to go out on a limb here and assume it was a black guy yelling at his kid, and not being a racist. Maybe it was a white guy, but that doesn’t sound like something a white guy would yell at their kid, even a racist.
While what you say is true, it doesn't really refute the comment you're replying to. It could have been a black, non-racist employee, but that doesn't mean it's okay to use offensive language in the workplace.
"clean work culture" = "It's not enough when a worker does their job, they also have to adjust their behavior to their employer's wishes, both at work and in their free time."