Many of us are in tech. If you exploited a security hole to gain access to an unpatched system, you are still guilty of circumventing the system. Many believe the tax code should be similar: avoidance==evasion.
In New York, a sliced bagel with a smear of butter is a taxable prepared food product. A uncut bagel with a side butter is tax free. Should I be a criminal for going the unsliced route if I wish to deprive the state treasury of $0.10?
GAAR replaces the predictable rule of law with the unpredictable caprice of whoever is currently the arbiter of what qualifies as 'avoidance'. (In practice, in a legal system that respects precedent, that would just replace legislation with case law.)
If you consider something a loophole, fix it. If the law is so complex that fixing loopholes seems untenable, consider simplifying the law to have fewer special cases.
Forget the law for a moment. A company profits from the infrastructure a country provides and therefore has at the very least a moral obligation to help financing it. It is a deal - company pays taxes, country provide infrastructure the company needs.
If a company then tries to avoid paying its share of the infrastructure, the company is breaking the deal. If doing so does not break existing tax law, that does not mean the company is in the right.
All this is of course fuzzy, but when a profitable company pays zero taxes, you can certainly not claim that you believed the amount of taxes you paid seemed reasonable to you. And the company should of course be held accountable for this even if it did not break any specific tax law. Not paying your share is a breach of the deal.
In the case we are talking about, the companies have to pay taxes but they exploit loopholes to avoid it. They may be not in violation of the letters of the law but they are in violation of the spirit of the law.
The moral obligation is to participate in the funding of the system you are profiting from. Making money by transporting your goods on roads built by the state, employing people educated in schools funded by state, and enforcing your contracts by courts established by the state but not paying taxes towards this system is wrong.
And this obligation does not go away if you find a trick to circumvent the written rules.
Of course, I am not a lawyer.