Tax efficiency/avoidance by politicians is so poisonous, not for the pure idea of tax avoidance being morally wrong, but because it leads to individuals who do not pay on the same terms as the people, controlling the people’s finances.
At least when a CEO avoids tax through their company they are controlling an entity that they have a significant stake in. If they incorrectly move too much money from one part of the company to another, it will go bust. Where as with Tax, when a company or its executives do not pay its full dues to the country in which they operate, the corporate or individual entities may maintain a financial benefit which may not cause an immediately noticeable detriment to themselves.
It comes though to a rather finer point, that when a tax avoider, or someone whose family wealth has come form off shore funds, is responsible for spending and controlling revenues in which they have no financial stake, poor decisions are easier to make, and lack of faith from the people (unable to avoid paying) can only follow.