I found a reference that suggests he did register the site in 2004:
Domain ID:D104838905-LROR
Domain Name:TEAPARTY.ORG
Created On:02-Sep-2004 18:54:10 UTC
Last Updated On:05-Apr-2009 00:31:29 UTC
Expiration Date:02-Sep-2011 18:54:10 UTC
Sponsoring Registrar:Network Solutions LLC (R63-LROR)
Status:CLIENT TRANSFER PROHIBITED
Registrant ID:37852062-NSIV
Registrant Name:Dale Robertson
Registrant Street1:ATTN insert domain name here
Registrant Street2:care of Network Solutions
Registrant Street3:
Registrant City:Drums
Registrant State/Province:PA
Registrant Postal Code:18222
Registrant Country:US
So again, it doesn’t look like he’s “late to the game” and “trying to take over the movement”.
Still haven’t found any posts on hot-air or elsewhere that indicate what makes him a racist, other than the sign.
He may have simply gotten lucky. The Boston Tea Party is famous in patriot lore. If he is the self promoter he certainly appears to be he would be looking for angles.