@Irishk,
Its standard military procedure to rescue downed pilots, if possible.
When they are forced to eject over hostile territory, the SOP calls for sending in a rescue helicopter, and supporting aircraft.
In that situation, the crew of that rescue helo doesnt have the time to find out who is approaching the downed pilot, and it is assumed that and ground forces approaching that pilot are hostile.
That assunption is made because most time the enemy does want to capture prisoners.
In this case, it was the US Marines that went in and rescued the downed pilot.
The marines are very good at that job, and they go in armed and ready to se whatever force is required to accomplish their mission.