Any conduct that demands someone does something unlawfully is unlawful. Taxes are laws and regulations. Not paying the taxes is unlawful, especially under 26 USC 7201. So the shareholders are not only demanding the company to break laws, they aid and abett such behavior, making them also liable together with the company as there is 18 USC 2:
(a) Whoever commits an offense against the United States or aids, abets, counsels, commands, induces or procures its commission, is punishable as a principal.
(b) Whoever willfully causes an act to be done which if directly performed by him or another would be an offense against the United States, is punishable as a principal.
It could also be inciting to violate laws. It is not a shareholder's right to ask for someone to break the law.