That, and when your order is pledged to keep peace and order in the galaxy, saying, “he’s too dangerous, so I’m going to kill him without a trial” seems just a teeeeny bit hypocritical.
I think his point was, “We cannot get him out of here right now, we need to kill him IN SELF DEFENSE, RIGHT HERE, RIGHT NOW.” There’s no way you could have gotten him in hand long enough to subdue the guy and put him underguard. Hell, Yoda couldn’t even take the guy down. I think it was more, “kill or be killed.”