I can agree with the spirit of your note, but the one thing that stands out as missing is the real reason that these huge corporations in any area of business thrive.
People are demanding these kind of businesses to exist.
Most consumers seem to WANT to have an establishment that they can readily recognize, wherever they may roam. While this is not inherently a bad thing, it does create the kind of megamonster that some of these corporations have become. While you can press the point of megaeats restuarants being evil, think about how some of the "mom and pop", or local joints have a rotting, fly-encased carcass lounging in the back room whilst hacking off portions for the evening meal. The corporations might be a greedy lot, but they do take into consideration the reality of backlash when it comes to cleanliness and health standards.
Lest you think I may be against your argument, let me state that I have enjoyed many of the non-corporate establishments and must say that I do enjoy the variety, individualistic flair, and uniqueness that these places offer. But, in truth when you see the "over 6 billion sold" sign is displayed on the golden arches, who is to blame, McDonalds...or the general public who seem to desire this establishment, no matter what the ethical argument may be?