The US government already provides security at events. Most venues such as stadiums either have their own private security or won't object to speakers bringing their own.
You don't need 10, 50, 100 dudes with AR15s to provide security at events. A dozen mall cops, or a dozen real cops, or a failing that the full riot squad, that's security. A right wing militia, that's intimidation.
The thing is we've already gone down this path in America a bunch of times. The Pinkertons, the worse examples of political machines, company towns, that one gold rush boom town run by a conman. Hell, the actual police for most of our history. Its awful every time. Democracy only works if the spooks and the soldiers don't show up to the electoral process and to the protests. Wannabe military cheerleaders, for this one thing, still count as soldiers.
I mean hell, this same conflict of interest has been playing out in the Middle East for years. People in Iraq actually need militias, that's part of why its so hard to externally impose democracy in Iraq and similar countries. Why would you want to bring all those problems to a place where there is no need for militias? And yes, there really is no need for militias, as much as the gun nuts would like to pretend the US is a war zone with a failed state it most definitely is not.