Incredible gall on this guy's part. He's lucky it didn't escalate. But he brings up an interesting paradox. No money for food but money for lottery tix.
There's a lot going on in that video, but whether you agree with his premise or not, this guy is a major ass.
I couldn't help but notice that one member of that group appeared to be a handicapped adult, and as such may be the person "buying" the groceries with the benefits card which one of the others might have handled on his behalf. I occasionally helped a neighbor of mine do her shopping when I was a kid, to include handling the purchase as she talked/moved very slow and most cashiers (and customers behind us) would lose patience waiting for her to handle the transaction. And if someone else in the group decided to buy lottery tickets at the same time, that doesn't automatically call in to question the legitimacy of their food purchase.
Things may be exactly as he assumed, or they may not be. Regardless, it isn't his business (taxpayer or not). And if anyone thinks being a taxpayer should allow for invasion of personal privacy (rather than redressing grievances to the government) then perhaps next time I am angry with the price of corn I will invite myself into the operations of the local farmers who get tax breaks from the government to support ethanol. Nothing too invasive, just make sure I am personally OK with the way they handle their operation. I pay taxes afterall.