I'm assuming you are a man that you can't see how threatening he was - but -
1/ language and tone was aggressive and threatening
2/ he used his size to intimidate by leaning in over the table
3/ wagging his finger to intimidate
4/ raising his voice
5/ sharp, violent movements - like when he turned back, he lunged rather than turned
6/ grabbing the child - laying hands on anyone in an aggressive manner is physical abuse/violence
7/ shaking the table
8/ issuing threats
Then there were the inherent aspects - his size, his age, the fact he was man, the fact he was White and Afrikaans. All of these contribute to the perceived level of threat from him.
If you want to see just how threatening he was - go back and watch the video again, and when he lunges across the table to shake his finger in the mother's face, watch the reaction of the child next to her - as he lunges the child flings his/herself backwards and cowers against the mother. Right there you can see how violent and threatening his actions were.
Here it starts just before he lunges forward across the top of the kids: WATCH THE CHILD!
[video=youtube_share;R_We_ieYgE4]https://youtu.be/R_We_ieYgE4?t=21s[/video]