It amazes me that no-one ever seems to say (not that I have seen, at least)...Isreal is a western, democratic state with nuclear weapons in the middle east.
It's basically a major power base for the west in the predominantly arab part of the world.
Anything else is a side arguement as far as I'm concerned.
This is the only explanation that spans parties and ideologies. Loosing this foothold would be detrimental to regional military and diplomatic influence.
We need to trust such a country to be judicious in their use of force, to not engage in any unnecessary conflict that puts both they and their allies at risk, and we want that country to be stable and share our values.
Israel is not demonstrating these qualities, at least not now.