He was hunting down guerrillas in a hostile urban area.
That's not same as an infantry engagement with uniformed troops on an open battlefield.
He was likely there because his special skills would prove useful in ferreting out high-value targets in that confusing and challenging environment.
Had he been killed by an IED while on a routine infantry patrol on the streets of Baghdad, your claims would make perfect sense to me.
But he was fighting in a very challenging situation where his special skills could well have made a very big difference.
"He was hunting down guerrillas in a hostile urban area."
That is what infantry do.