Writing in his column for the Daily Mail, McCullum said that by not withdrawing the appeal, Smith had revealed his immaturity and may live to regret it.
In his view, Stokes was merely trying to protect himself by sticking his glove out and the Australians decision to appeal for obstructing the field in those circumstances wasn't right.
McCullum added the situation had presented Smith with a chance to make a statement about how his side could play, but that he will one day look back at Stokes dismissal "and realise he missed a great opportunity to strike a blow for the spirit of cricket."
While insisting he was not trying to frame the Black Caps as being holier-than-thou, he wrote that none of the current members of the New Zealand side would have appealed in the first place.
Winning is important, McCullum said, "but the longer you play this game the more you realise that some things are too valuable to spoil."
The Kiwi skipper insisted he was speaking from experience, comparing the incident to a test match where he ran out Muttiah Muralitharan while he was celebrating his partner Kumar Sangakkara's century. Looking back McCullum said he would act differently now.
He added his belief that former Australian captain Michael Clarke and England skipper Eoin Morgan would have both withdrawn the appeal.
McCullum finished by cautioning England against getting too emotional about the matter, saying he regretted the Black Caps' gleeful celebrations upon winning a game at The Oval off the last ball, after they were left fuming over Grant Elliott's controversial run-out.
