Corporations are so ubiquitous that it's hard to blame anyone for using their products, even if someone hates what corporations do and believes they should change their way or be gotten rid of.
Look at it this way, anyone in a country dominated by an authoritarian, totalitarian government will almost certainly have to utilized government services and products in the process of protesting or rebelling against the government. Is there hypocrisy there?
My own belief is that in just about any matter where private business and commercial motives should exist, a cooperative would be preferable to a corporation. There are also areas that are currently run solely by private business that I think should perhaps be handled publicly anyway. Right now I can buy things from a corporation because it's my only real option, but still be aware that I'd prefer the alternative and work toward that goal.