No one is claiming that it's illegal. People can give up their rights as long as it's voluntary. It's generally seen as wrong or socially unacceptable to require that though.
Do you have a legal precedent to point to? The Bill of Rights (the first 10 amendments to the constitution) didn't even apply to state governments until the 14th amendment.
For revoking corporate charter? Every jurisdiction which grants them also already reserves the power to revoke them. E.g., Delaware: http://codes.lp.findlaw.com/decode/8/1/X/284