Americans may be shocked to discover that given the downward trajectory of the US at the moment, for many international travellers this is yet one more reason to choose somewhere else over the US. It's hardly extreme to avoid a country that keeps providing reason after reason to avoid it.
Especially for people who have been outspoken about the US' illegal wars and various war crimes.
It's rather extreme to refuse to visit the US because of just that. However, refusing to visit countries that do things you don't agree with is a rational decision. I have a friend who declared he would totally refuse to visit North Korea -- why do you want to spend your money to enrich a shitty country and government? More practically, why do you want to spend vacation time being pissed off if you have literally hundreds of other choices?
Especially for people who have been outspoken about the US' illegal wars and various war crimes.