I'm not sure why any successful photographer would feel the need to be arrogant on a forum made up of mostly hobbyists, but often, those concerned with technique and science don't get on with the artists.
The person who commented about wanting to 'emulate' a photographer may not understand that this person could have spent his whole life developing his style, technique and art. His rudeness may have been a reaction to somebody trying to find out his secrets. In the same way, those concerned with photography as an exact science may be rude to very talented photographic artists with great eyes, natural ability with a camera, but lacklustre technique. The 'scientists' might be miffed that all their time spent learning the science hasn't paid off so much in terms of compelling photography.

This is without a doubt the best resource for the craft, with lots of very knowledgeable people always willing to share, but the artists tend to get what they need from APUG and carry on with their voyage into expressive photography.