The nation was founded on the principle "The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants". The question is whether an increase in political violence reflects negatively on the citizenry or negatively on the ruling class; political violence isn't necessarily immoral if the ruling class is sufficiently corrupt/authoritarian.
>The nation was founded on the principle "The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants".
No, it wasn't. That is a quote by Thomas Jefferson in a letter he wrote about Shay's Rebellion - one man's opinion, not a foundational legal or moral principle, and not every founding father agreed with him. While Jefferson was sympathetic to the spirit of revolution that brought Shay's Rebellion about, he also condemned it as having been the result of ignorance. As is often the case with pithy quotes from the founding fathers, the speaker and their opinions are a lot more nuanced than the quote, stripped of all necessary context, is meant to imply[0].
As to whether an increase in political violence reflects negatively on the citizenry or negatively on the ruling class, Jefferson (a member of the ruling class, mind you) would likely have seen it reflecting negatively on the citizenry, as reading the letter in which the "tree of liberty" quote appears[1], it's clear that Jefferson draws a distinction between the necessity for the potential of rebellion and the commission of political violence itself. In fact, just before the quote you provided, Jefferson says the answer to such rebellions is to "set them right as to facts, pardon and pacify them," not to support them on principle.
The fact that both are going up is not a good sign. It actually really worries ne now that I think about it.