So, just so we're clear, it's not OK for others to do it, but when it's his team(s), it's OK? And no, I've never heckled a professional athlete. Or any athlete, other than my friends.
But...going back to your original quote. He was upset that RTCs provide opportunities for people, many of whom in turn help make American athletes better?
As an example, Bekzod and Dake trained together at the NLWC quite a bit leading up to Tokyo, where they both won bronze at 74kg. Dake beat Chamizo, and was quite effusive in thanking Bekzod for helping him prepare. Was having a world class 74kg training partner a bad thing, because it was a foreigner?