Phil Mickelson told his critics to "toughen up" after admitting he deliberately hit a moving ball to gain an advantage in the third round of the US Open.
Mickelson, who was already four over par for the day on his 48th birthday, badly overhit a putt on the 13th green which was set to roll off the putting surface.
The five-time major winner prevented that happening by running after the ball and hitting it while it was still rolling, a breach of rule 14-5 which incurs a two-shot penalty.
Former US PGA champion Steve Elkington called for Mickelson to be disqualified, writing on Twitter: "Absolutely 100% conduct unbecoming ... hes trying to embarrass the USGA DQ his ass."
And LPGA player Christina Kim wrote on Twitter: "I have never done anything so ghastly. I'm curious to know what sort of "logic" caused him to do that. I'm in shock."
However, Mickelson, who eventually made a 10 on the 13th in a round of 81 which equalled his highest score in the US Open, said: "If someone is offended I apologise, but toughen up.
"Knowing the rules is never a bad thing. You always want to use them in your favour. I know the rules and the ball was going to go off in a bad spot. I did not feel like continuing going back and forth. I would still be out there potentially.
"I've wanted to do it many times before and finally did. I should have done it a couple of times on 15 at Augusta. That would have saved me a shot or two back then."
Mickelson and playing partner Andrew Johnston were laughing about the incident as they walked off the green and Mickelson added: "How can you not laugh? It's funny. I just wanted to get to the next hole and did not see that happening without the two shots."
Commentating on the incident for Fox, former Ryder Cup captain Paul Azinger said: "That's the most out of character I have ever seen Phil. I think he just snapped. I'm sure he is going to regret that."
And two-time US Open champion Curtis Strange added: "He will feel some embarrassment because there are a lot of people and kids watching that really admire this guy."
David Fay said he would have "lobbied for disqualification" if a similar incident had occurred while he was executive director of the USGA, adding: "I think the current language of [rule] 14-5 is too friendly."
Asked why Rule 1-2, which covers a ball being "influenced or deflected" and can lead to disqualification for a "serious breach" was not invoked instead, John Bodenhamer, the USGA's senior managing director of championships and governance, said: "Phil didn't purposely deflect or stop the ball, which is talked about in the reference under Rule 14-5. He played a moving ball."