Do you really think MLK Jr. didn't want to punch those cops in the face that were beating people at his marches? But he had emotional IQ, discipline, and effective organization. The current crop lacks all of that and the results are showing it.
Go look at news coverage from the period, he was denounced as an agent of chaos and blamed for riots all the time. Read history, not the anodyne postcard version of it.
His behavior at his marches is well documented. He wasn't setting anything on fire or throwing rocks at police. One way brings the American center to your side, the other pushes them away. Those who ignore this do so at the peril of their own causes.
Yes, the parent's point is that despite being restrained as you describe, the establishment still tried to paint MLK as a provocateur. Which speaks to my point that the status quo faction is always going to frame protestors this way in order to undermine them.
Yes and the videos of his peaceful marches and the brutality of the police ended up discrediting the establishment propaganda against him and bringing the American center to his side. It's the most historically successful strategy in activist history, but no one wants to do that because it doesn't feel good in the moment.