The powerful people that set the rules have made it unacceptable to kill powerful people.

Powerless people? Into the meat grinder!

Would you say the same if iran killed trump?

This isn't the gotcha you think it is. Most people in my social circles have a bottle waiting for a date.

I cannot confirm or deny that I would say the same thing

They're civilians, for one.

Are they? In most countries the head of the state is also army's commander-in-chief.

Yes, but these are traditionally not treated as actual soldiers, but civilians commanders-in-chief-in-name-only.

Only because of professional courtesy between powerful assholes. I have far more sympathy for an infantry grunt from literally any country in the world than any head of state.