I completely agree with your position and please forward as necessary. Anyone can buy a complete uniform from Sporty's Pilot Shop.
One time I bought a $5 Starbucks outside the secure area and was refused entry unless I disposed of the coffee. I mentioned I was a crewmember and they said I had to be in uniform to take the coffee in. To make a point I went into the nearest mens room, threw on my uniform and went back through the same line with the same TSA agent and my Starbucks! After I was through I went into the next bathroom and changed back into my civilian clothes. I know, a lot to go through but I proved a point.
Another side note: At some airports I've been asked by TSA for another form of government ID in addition to our FedEx ID. Regular passengers get through TSA on 1 form of government ID such as a drivers license or passport. If I have to show another form of government ID, why even bother showing the crew ID, especially when deadheading in civilian clothes?