Whoa... hey... calm down

The point the filmmaker was trying to make was that the way that McD's operates it's marketing campaign is to have children associate it's food with good feelings and this happy-go-lucky clown making life better for all the children he meets. Thus, with enough brand imprinting, the children come to associate this image with positive feelings. Get children to do this, and you got yourself a captive market. Captive markets mean established and constant revenue for the company.

The image he used of Jesus was quite possibly the most iconic image of him that I've ever seen, but that's irrelevant.

It was the same thing as later in the movie, he tried to get some people to recite the pledge of allegiance... It took them like 4 tries, and every time the group of them screwed up... he asked them if they remembered the Big Mac song, and one of them was able to recall it perfectly.

Again, his point is that the way McD's markets itself, it ingrains it's image and it's slogans so deeply into our minds in a way that we can't help but think of them when we think of cheap and fast food. And that they intentionally start this marketing from a young age to draw us in and make us customers for life.