Morals and ethics have no say in determining whether to pay taxes -- if you pay too much then the government complains, if you don't pay enough then the government complains. Where exactly does right and wrong fit into this equation?
There are no mental gymnastics in determining how much taxes you have to pay, the only thing that matters is how much you pay.
>Morals and ethics have no say in determining whether to pay taxes
Morals/ethics do have a determination whether the concept of tax is ethical or not, which would then determine the ethics of avoiding said tax. If you take the position that tax is ethical (as a member of a society...) then it is at least on the surface unethical to avoid the intended tax rate (shifting burden, freeloading, etc).
There are no mental gymnastics in determining how much taxes you have to pay, the only thing that matters is how much you pay.