“tautological”
Do you know what that word means? I don’t think the headline is rhetoric.
He is saying that it is tautological because the fact that they were killed establishes that they were doing something dangerous, so for the headline to say that they were doing something dangerous gives us no additional information. So I think it is a correct use of the word. (Now, one could phrase the headline differently such as: Marines Killed While Doing Job Known to be Dangerous... and that would not be tautological because that would actually be telling us something that we would not know from the mere fact that they were killed.)