The actual principle behind taxation is that we siphon some money off to pay for the common needs because the free market is great at allocating the correct number of shoe stores to a town and worthless at making it possible to live in that town.

Taking from foreigners so long as it isn't so much that they are discouraged from doing business is a plus in that it increases the welfare of your people at the expense of the other guys people.

This is the actual theory of taxation and everything else is after the fact justification.