How many lives do you think Trump will destroy? If the answer isn’t “a lot”, you haven’t been paying attention. His supreme court justices from his last term have already started racking up one hell of a body count.
Would you object to police officers gunning down a mass shooter rather than allow them to continue taking innocent lives? How sacred is a single life against the lives of their many potential and actual victims?
From a purely ethical standpoint, it’s hard to argue that killing fascists is anything other than a net moral good. At the end of the day, it’s taking one life to save many, something that we accept as an unfortunate moral necessity all the time. Obviously, we prefer to exhaust other options first, but ultimately we still accept the use of violence to protect the innocent when strictly necessary.
(I am, of course, speaking purely in terms of ethical hypotheticals here)