> I read it as something like 'are required to by law.'
I would have said 'have to' to be required by law. 'Should' implies a moral code, a desire to do right and good. In this case, Google absolutely 'should' pay those taxes.
> I'm curious, what was your reasoning for paying $500 more than expected? And in what way did it "not make sense" to not do that?
If you have more money than necessary, and you know that others don't, and you know that a good portion of your taxes goes to helping others, the rational thing to do could be to help out and not attempt to claim every tax break and benefit you could. I'm not saying that's always right, I'm saying it can be rational for people to do it.
Paying as little taxes as possible to avoid jail is absolutely not the rational move for people or corporations. This is a classic tragedy of the commons: if people and companies paid taxes as due, we would all be better off for it. The rational move is to fully pay all expected taxes, not use offshore secret hideouts to avoid improving your own country.