https://www.adl.org/murder-and-extremism-2018

'In 2018, domestic extremists killed at least 50 people in the U.S., a sharp increase from the 37 extremist-related murders documented in 2017, though still lower than the totals for 2015 (70) and 2016 (72). The 50 deaths make 2018 the fourth-deadliest year on record for domestic extremist-related killings since 1970.
The extremist-related murders in 2018 were overwhelmingly linked to right-wing extremists. Every one of the perpetrators had ties to at least one right-wing extremist movement, although one had recently switched to supporting Islamist extremism. White supremacists were responsible for the great majority of the killings, which is typically the case.
Deadly shooting sprees were a major factor in the high death toll. Five of the 17 incidents involved shooting sprees that caused 38 deaths and injured 33 people.'

While those aren't enormous numbers, mass killings have an influence on society far greater than simple numbers, IMO. They make people afraid...they divide people and anger them. Very dangerous to society, and a good reason for (among other things) much better gun control.

Nevertheless it's clear that the danger comes from the Right in America at present.