Phil,
Some people just like to feel superior to others and cycling seems to have gotten a large part of that group when they were parceled out. You naturally feel protective about your bike (rightly so, in my opinion) and want to defend it when some thoughtless jerk is being really smug. Just laugh it off and move on, I've learned that these are really small things in life, I've been written off while laying in a hospital bed several times over the last 13 years, a jerk being a jerk about your saddle is just not worth the effort or worth ruining a good ride. Brooks is the original, cannot question that fact, Fuji Belt are really good saddles, but they are a take off of the original, its just the way it happened. Ride Lots and Ride Safe.

And, if he wants to pick off some nits, just tell him he is riding a knock off bike, it is just a take off of the "original"

Bill