You must look at it from the perspective of the Oligarchy: Wars, regime-changes, support to "moderate" forces, spying on the world just cost money. And you cannot afford all that by only taxing those at home. You need every dollar. So, you tax the expats (8.7 million of them!). They are abroad to work after all - they MUST have earnings. As an alibi for your new revenue source, you pass a new law (Fatca) while saying…
If you asked "Average Joe who is overworked, has two jobs and CC debt" how much he was concerned about the great injustice of requiring expats earning >$100k/yr in low-tax nations to make up the tax difference, you wouldn't get much sympathy. However, it wouldn't be very honest to attribute his lack of sympathy to apathy. I imagine he'd care, and that he'd find the present arrangement agreeable.
I wrote "the Average Joe cannot think", not "the Average Joe doesn't want to think". Other than that, I agree.