"It's ridiculous for O'Neill to claim the credit for the fatal shot as we probably never will know and don't need to know," said Gilliam, a security consultant, saying his views reflected those of many Seals.
"He served with distinction, he had a great career and he was a great operator. But he went from hero to zero in the Seal community when he started using his career to cash in and draw crowds as a speaker. This reflects terribly on all of us."
Gilliam also expressed fears O'Neill had made himself and his family targets for revenge attacks by Islamist extremists.
"He's put a bullseye not just on his back but on those around him by identifying himself. If I heard he was coming to give a speech at my workplace, I'd call in sick."
It is not known if O'Neill has taken extra security arrangements or will be provided with protection by state or federal agencies after choosing to identify himself.
O'Neill has not, however, gone into hiding since disclosing his name. He gave a talk to a chamber of commerce in Tennessee this week, during which he related combat stories but did not mention the bin Laden raid.
Gilliam was similarly critical of Matt Bissonnette, another Seal on the raid who has taken credit for shooting bin Laden.
He also denounced Joe Biden, the gaffe-prone vice-president who first revealed it was Seal Team 6 unit that killed bin Laden, and Leon Panetta, the CIA chief who gave scriptwriters full access for research on Zero Dark Thirty, the film about the raid.
"Security is being compromised by the release of information that should not be public."
