While I was listening to this, the sense that I came away with is that Alex is trying to threaten Trump. Essentially, what's happened is that the two of them don't agree on the issue of the vaccine, and on some level, I suspect that Alex knows that the supposed evidence he's presenting is shit, so the last option left to try to get Trump to help him expand the grift is to extort him. Alex isn't saying that if Trump doesn't change his tune on vaccines, the natural result of that is that Trump's legacy will be that of a monstrous baby killer. He's saying that if Trump doesn't change his tune on vaccines, Alex will start yelling about how Trump is a monstrous baby killer. That's what's going on.