1) Never sell or buy goods in Europe. Make what you need, and sell to the natives.
2) refuse the tax hikes - as long as the boycott isn't on a commodity you'll want to buy or sell in Europe.
Even if you only *sometimes* buy or sell goods in Europe, that can dramatically slow down the speed of tax hikes. Lately I've been trying to avoid European commerce until after I've sold off all the available treasure from exploring. Votes not in yet on whether that really makes economic sense or not.