All musicians sell out. That's what the Tool song was about. Not only that but we all sell out. Every person who is a fan of anything sells something of themselves to be a fan. To buy a product. To wear a particular brand.
Every sports person is a sell out when they endorse products. No one seems to care.
Be a musician and do something 'mainstream' or become well liked and all of a sudden you're selling out.
Strange world we live in with our expectations on people. Damn musicians wanting to make money and all that.