Only if you have a pretty odd ethical code, IMHO.
No, it's pretty sound. Pay some taxes but not more than is reasonable.
Why does that strike a moral pang in your heart?
If the taxes were 100% of all earnings would you claim they should be paid?
There obviously is some value for which taxes are too high. It's too grey a line to claim anyone is crossing it unless they pay zero, and sometimes not even then (but, Apple does not pay zero taxes anywhere).
Some of us believe that corporations (like citizens) should have an ethical obligation to pay tax to the country they use the infrastructure of.
Apple does pay taxes in every country. They pay taxes in the U.S. They pay taxes in Australia. They pay taxes in Ireland. They just move where some of the income is declared in a way that the countries involved agree is correct. So how is Apple shorting Australia when they pay more in taxes than they consume in services?
In any worldwide company, it can make a lot of sense to shift where income is declared. If a device is assembled in a different country with parts made by still other countries, why does it make sense that 100% of the profit from every device sold in Australia is declared in Australia?
IMHO, this is as unethical as using the WIFI connection of your 80-year old neighbor cause she didn't know how to set up the security correctly.
That's unethical because you are literally stealing from her bandwidth cap, outbound connection speed, and potentially getting her in trouble if you are using any illegal torrents. But Apple is stealing from no-one. If even the Australia tax people don't think Apple is, what gives YOU the right to claim Apple is stealing just by shifting where some income is declared?