Maybe the differences are:
1) Mel Brooks hadn't just written an article for the BBC saying we shouldn't make fun of Nazis
2) He was lampooning the Nazis, whereas this Asda thing just seems to be "lots of plebs go to Asda. If we spike their pizzas, the world would be better. A-ha-ha-ha!"
If it really was an attempt to show the Waitrose shoppers up for their snobbery, it could have been more clearly signalled...