Because only corporations and billionaires are allowed to commit it?
Thinking it's wrong to advocate fraudulently billing in a poor country to avoid a small charge, does not preclude thinking it's wrong for corporations or billionaires to commit fraud.
It is not just about thinking that corporations/billionaires are doing something wrong, it is also about them getting away with it, governments doing nothing about it and being powerless yourself to do something about it. If this world rewards the rich cheating for example by using tax havens, why not cheat themselves out of some dollars a month by using a 'cheap haven' yourself? Seems fair to me.