There's something more to the story, which is what was expressed above. It appears that you also have no knowledge of the specific incident- just unfortunate experiences with your children. Simply, you and I are going to see the original claim through our own lens.

I'd believe that his son was cuffed twice by police - just not that "it's because you're black, son". I would imagine it's possible that there was some sort of prejudice that led a cop to cuff him. But even if that were the reason, I seriously doubt that the cop is going to tell him it's because of his skin color.

I'd also think it's possible that the cop doesn't explain why he's cuffed, so he has to make his own assumptions, the obvious one being based on race.

But the fact is me - you - we don't know.