A lot of the debate over whether Israel (presumably) is committing acts of terror in Iran by killing scientists hinges on the question of whether these scientists are actually civilians or not. Commentary's Jonathan Tobin, for instance, argues that it's not terrorism because these scientists were helping Iran build a weapon of genocide:
But you need a particular form of moral myopia not to see that heading off a potential second Holocaust in the form of an Iranian nuclear attack on Israel or the nuclear blackmail of the rest of the Middle East is not a form of terrorism. Anyone who believes Iran should be allowed to proceed toward the building of a nuclear bomb has either lost their moral compass or is so steeped in the belief that American and Israeli interests are inherently unjustified they have reversed the moral equation in this case. Rather than the alleged U.S. and Israeli covert operators being called terrorists, it is the Iranian scientists who are the criminals. They must be stopped before they kill.
I think if you accept Tobin's logic, then obviously killing any Iranian, civilian or otherwise, connected to the country's military-industrial apparatus is justified since the alternative is a nuclear attack on Israel that will leave potentially hundreds of thousands of people dead.
But there's ample reason to believe that Tobin's logic isn't all that logical. Consider that Iran is believed to have had weapons of mass destruction since at least the Iran-Iraq war. If Iranian leaders were truly irrational and not concerned about a devastating retaliation, they could have launched a biological or chemical attack against Israel.