The IRS is a violation of individual rights and should be dismantled. It is not in anyone's true self-interest. People who are actually pursuing their own self-interest are hurt by it, only those that are not receive the "benefits" of it.
Of course corporations should enjoy freedom of speech, etc (because to curtail those necessarily curtails some individual's freedom), but do they get to vote? No.
The income tax also has a secondary effect to generating revenue: it implements control and enables targeted abuse of undesirables with a big dossier of filing mistakes.