You cant call BS, I have seen it.
What was the manufacturer, the round count and exactly how does mild steel "tear up" tool steel?
I'll concede that the extractor will eventually wear out, it will do the same with brass, but I've never seen any evidence that steel cases wear the extractor any faster than brass cases. Between three guns I'm currently using for training guns they have in excess of 30K of steel case between them since mid 07 with no signs of excessive wear. One of them is a Glock22 converted to 9mm that has twice shot 1800 rounds in a weekend class with no cleaning.