It's not execution; in many/most states, you are allowed to defend life, health and property with deadly force. It may be getting watered down these days due to unfavorable public opinion, but a law in the books in WA is/was, iirc, that you can use deadly force to prevent a felony.

In modern law the use of deadly force is only allowed to prevent a felony IF that felony create a substantial risk of death or bodily harm.

I mean, get real. You can't just shoot people for breaking windows or stealing. The fact that this is unclear to anyone is appalling.

Why, from the first principles, though? It's a slope and not a switch, but even in the case of "regular" crime, I'm not entirely convinced someone showing willful, unambiguously intentional disregard for basic social contract/others' negative rights, has full claim to the same rights, i.e. full moral value.

In this case we are talking about trying to achieve political means via violence. The kind of people who do that outside of very extreme circumstances definitely renounce their moral value as human beings in my view. It's not that they /should/ be shot as a punishment or something; it's more like dealing with malarial mosquito - the evil is on the level where ends justify the means.

"The kind of people who do that outside of very extreme circumstances definitely renounce their moral value as human beings in my view. "

Your logic could be applied to any number of movements, including the Women's Suffrage movement, the Civil Rights movement, the Revolutionary War, and thousands more.

Excluding the Revolutionary war, it would only characterize a small subset of these movements, often acting explicitly against the wishes of its spiritual leaders. It's not really about values; I am an atheist and I believe that the world would be a better place without religion, but if someone firebombed an empty church out of the same impulse I'd still place them in the same dehumanized category.