O'Brien told Irish radio that over-training before the first and the final tests against the All Blacks had cost the touring Lions the chance to win the series earlier this year. The series was drawn 1-1.
The comments were condemned by media pundits and former Lions players, and Gatland said they had taken a personal toll.
"I don't know what planet he is on saying that," the New Zealander told British media. "Those comments were disrespectful to New Zealand.
"You watch how hard the coaches and the backroom staff worked -- they worked their absolute nuts off -- and then to have someone come out and make a comment like that ... it really, really did hurt.
"I wouldn't subject myself to that again. It took the gloss off the tour."
Gatland conceded he would have done some things differently with the benefit of hindsight.
"No one has ever in the history of the game taken on a tour of that magnitude or difficulty," he said.
"Did we learn as coaches from that experience? Would we have done some things differently? Of course, we would. That's part of coaching, part of the experience."
O'Brien's critique did find support from Billy Vunipola, although the England back rower played no part in the tour after pulling out to have shoulder surgery.
Vunipola told British radio the Lions would have whitewashed the All Blacks if Eddie Jones had been in charge.
"I've never had any involvement with Billy and that's a disappointing thing when you get people coming in second-hand and making comments as well," said Gatland.
The Lions, who next tour South Africa in 2021, inflicted the first home defeat on the All Blacks in 48 tests with victory in the second match in Wellington and won huge admiration for pushing the world champions to the wall.
But Gatland said he did not enjoy the tour of his home nation.
"I hated the tour. I just hated the press and the negativity in New Zealand," he said.
"I'm done. When I look back on it now, there were a lot of things that were satisfying and what an achievement it was, but it was tough work."
(Reporting by Ian Ransom in Melbourne; Editing by Greg Stutchbury)
