Should Buddhists avoid Amazon and Starbucks out of concerns about tax avoidance?
I think the answer is No. You can, but due to your personal views and believes, it has nothing to do with Buddhism, from a Buddhist's perspective you should take care of your actions, they will receive the results of their kamma (if any). Focus on what you do and left undone as the Buddha taught.

Another thing is that these days almost 99% of the companies do some kind of tax planning that involves similar practices, you just don't know it.

In an extreme example imagine if someone says: I will not pay taxes because the government is corrupt, that is wrong, as a citizen you should pay taxes and the politicians will face, sooner or later, the consequences of their actions.