Actually, sanguine fits quite well.
TJ was calm and unflappable about a situation in which other Founders were flipping out. Which is what sanguine means.
The meaning comes from the old medieval theory of the "four humours" - a sanguine person has a predominance of red blood (sanguis) in his body and hence is florid of complexion, jolly, and busy. From that, "sanguine" has come to mean "optimistic" or "hopeful".
What the author meant (I think) is that because Jefferson was in favor of rebellion he was bloodthirsty - i.e. "sanguinary". That fits better with the tone of the article - that bloodletting in the streets is justified as rebellion.