The surrender rule is needed. Here is a story where the rule was not enforced properly.
My friend flanked the other team. He was behind a rental's bunker and called for him to surrender with his barrel about 5 ft. from the guy. The guy turned around and pointed his gun at my friend and started yelling for him to surrender. The ref just stood there dumbfounded. After about 20 seconds he stood up and started firing repeatedly into my friend's chest. My friend responded with a much more potent string into the other guy. This went back and forth until the other player ripped his mask off and charged my friend. He was hopping around calling my friend a racist, homosexual, etc. (much more explicit than that
The situation continued when we got back to the field's store. He had a group of friends that wanted a gang fight due to what they perceived as a racist attack. After about 20 minutes and an embarrassing scenario for the field, they were escorted away and told us to meet them at the Hooters up the street.
There was no meeting, end of story. The staff did a good job of defusing the situation afterwards. Things could have been very ugly with several people there with CCW's and the other group of guys wanting a racially fueled fight.
All of this could have been avoided with a clearly defined surrender rule and a ref ready to enforce it.