As the original author of the letter, it's worth mentioning that the original version did mention that some conservatives – Evan McMullin and some folks in Congress – have spoken up.  I know that many on the left have tried to take a good look at whether our words and actions encourage violent activists.  However, you don't see folks at the top trying to make excuses for violent anarchists ... pardoning Joe Arpaio, though, strikes me as the epitome of excusing egregious behavior.