You don't need to present your DD214 to anyone. He can either take your statement of service or not.
You don't need to apologize; if you were a Marine and reached the rank of Major, then you have every right to "wear" that "title." As a veteran, myself, I can chose to include my service information on what ever medium I wish - so can you.
I'm sure USMC_Trev wouldn't appreciate someone else telling him to change his forum handle and accuse him of stolen valor without due cause.