GregJ, so dwaswad goes to the show, takes some pictures, posts them online, takes the time to label the pictures and share them with the car-interested-internet world. The only thing you have to say is something snarky and snobbish? Why not simply suggest that he may have mislabeled the Packard? For example, you could have simply said:
“Dwaswad, great pictures. Thanks for posting/sharing. I believe the shot you identified as being a Duesenberg is actually a 1934 Packard Phaeton. Keep up the great work!”
Would that have been so difficult?