It always takes two to tango. Crash is correct when he(?) asserts that if people did not buy McDonalds' products, McDonalds would die a well-deserved death.
Karm is correct in pointing out that nobody is holding a gun to the head of McDonalds' CEO, and that he can stop targeting children and producing garbage food, yadda yadda yadda...
So, who bear more responsibility, the addict or the pusher? When both are adults, they are equally responsible if they are aware of the issues involved; it's safe to say that many McDonalds' customers, and even some McDonalds' executives, don't put two and two together with regard to where the McCrap comes from, how it got there, what it does to you, etc. We're fighting years, even centuries, of brainwashing. However, once both sides know -- and anyone who visits McSpotlight and reads the information here can no longer claim blissful ignorance -- then both are equally responsible.
Yet, McDonalds aims it's seductive marketing at children, who don't know any better. Weary parents must therefore either deny their crying children a Happy Meal and feel like heels, or give in and feel like heels -- they lose either way. And once children and teens become old enough to venture forth unchaperoned into the world and spend their own money, marketing and peer pressure can easily undo all that a parent has striven to teach their children, and McDonalds sells another burger.
Given all this, while both side bear responsibility, I'd say the greater burden of guilt lies squarely on the evil clown's shoulders.