We don't have to use guillotines if we can, with much less violence (ideally, none at all), destroy the upper class's ability to function as a class. It's not that I care either way for their lives on an individual level; but, as a student of history, I recognize the horrible downstream costs of even justified applications of violence. This is doubly true in the US, where it's the biggest assholes (the far right, many of whom openly fantasize about a bloody civil war) who are most prepared to go that way.
It will not take a whole lot to destroy the elite's ability to function as an elite, and once that is done, they are nothing but a deservingly disliked tiny minority that have lost the support on which they rely (both individually and collectively) in order to function. In practice, the efforts will probably not be entirely nonviolent (they will certainly be unlawful, and one must be prepared to return fire when fired upon) but the bloodshed can be kept to an absolute minimum so long as focus is kept where it belongs.