I didn't see the video. I do believe from comments that the mother reacted badly and that it did her no favours at all, and was a bad example for her child.
What I said is that it is impossible for most of us to know how the cumulative and repetitive effect of racism leads to that unfortunate form of response. If you have close friends and family who have been constantly and repetitively stopped, questionned, often in a very confrontational was, deliberately 'pressing the buttons' - perhaps you would understand this better. She was wrong to react this way- but we have to try and understand why.
'Cry racism' blimey indeed.