This looks like BS or worse to me.
I’ve put in decades on a family dairy farm. You are right about the vast majority of farm owners and workers—not because of concerns for milk production, but for the same reason most people don’t abuse their dogs. That said, there are bad apples.
Just my guess from the video: the owner kicking the cow in the head was doing so to get a lame or otherwise injured/ill cow up. Because it hurts the cow in such a circumstance to get up, it may take some sort of aversive action to get her to do so. But it may also save the cow’s life: muscle atrophy for a cow that is down can quickly lead to her end. That said, the owner took a callous and nasty approach to it, suggesting to me that he may have set the tone and had the indifference that made the improper hiring and training of the workers videoed quite possible.