Willie Nelson has opted to pull out of a planned SeaWorld gig in 2014 due a simple fact: He has problems with how SeaWorld treats its animals.

"I don't agree with the way they treat their animals," Nelson, who was due to perform at a Bands, Brew and BBQ event, told CNN on Friday (Dec. 6). "It wasn't that hard a deal for me."

A SeaWorld rep previously said that Nelson had canceled due to scheduling conflicts, although the singer did not say anything about itinerary issues when he discussed his decision. Rather, Nelson has an issue with SeaWorld's treatment of its whales and other marine life.

"I understand that there are some natural-habitat zoos out there, which is probably OK," the legend adds. "But what they do at SeaWorld is not OK."

SeaWorld has come under fire recently after CNN aired the 'Blackfish' documentary about the trainer who was killed by Tilikum, a captive orca. The film also explores the history of the whale in captivity, revealing that the creature was harassed by other captive whales and left in a tank for hours, factors which may have heightened his aggression. The film also spotlights his majesty and intelligence.

Nelson did admit that outside pressure, via petitions, factored into his decision to pull out of the gig. However, it was the protest that his granddaughter showed him that got to the country icon, 80. That petition had "people she knew asking me not to play this venue," Nelson reveals.

Another petition collected 9,000 signatures and spotlighted the singer's "activism for animals, the environment and other good causes." That made him realize that he could not go through with the show, but in the end, he canceled because he felt it was the right thing to do in his mind.

The singer admits he thinks some zoos can be cruel with their treatment of animals, which is why he understands a captive monkey "wanting to throw stuff at you."

Nelson is not the only artist to pull out of a SeaWorld gig planned in the new year -- both the Barenaked Ladies and Heart have canceled shows, citing similar reasons.

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