American Imperialism at its finest. "Since we're the best country in the world, you couldn't have possibly become rich without us, and therefore you must pay to leave us!"
The parent never proclaimed America was the best in any regard, nor hinted at such an attitude.
Nobody needs to think their country is the best just to implement negative tax policies. All it indicates at a base level is the desire to maximize tax revenue. That goes for countries with extremely high tax rates on high income, which is semi-common in the developed world: it does not necessarily mean those nations must think their country is the best, therefore they can tax the rich whatever they like and said rich won't leave.
a) cole seems to specifically be talking about very wealthy people who did work and earn money in the US but who renounced citizenship largely for tax purposes (e.g. Eduardo Saverin)
b) cole talks about the foreign-earned income exclusion, which is misplaced (for people like (a) this is very different from income earned on investments and for wealth which is subject to the exit tax)
There's a smattering of outright incorrect things too like having to pay taxes for 10 years after renouncing.