MADISON, Wis. (AP) -- A Wisconsin golf course owner who advertised nine holes of golf for $9.11 to mark the anniversary of the Sept. 11 terrorist attacks apologized Tuesday but said he would keep the club open despite a backlash that included death threats. Tumbledown Trails Golf Course near Madison advertised the special in the Wisconsin State Journal newspaper on Monday, saying it was intended to commemorate the 12th anniversary of the attacks that killed nearly 3,000 people. The discount, which also included 18 holes of golf for $19.11, was good for the anniversary on Wednesday only. News of the offer spread on social media and the golf course's Facebook page was overrun with negative comments. Owner and general manager Marc Watts said he received death threats and threats to burn down the family-operated public golf course. The sheriff's department sent a deputy there Tuesday, and Watts said another officer will be back on Wednesday. "We're a little hurt by the fact that people are putting such a negative context on this," Watts said. "I thought people would appreciate it." The promotion actually began two years ago, on the 10th anniversary of the attacks, and until now was warmly received as a way to ensure people never forget the tragedy, Watts said. This year, after the newspaper ad circulated on social media, Watts said the club's phone has been ringing off the hook. Watts apologized Monday night on Facebook and was personally fielding calls on Tuesday, saying there was no intention to cause offense. He considered closing the 20-year-old golf course Wednesday because of safety concerns but decided to keep it open. "We could close, but then all these people with their negative attitudes, they win," he said. Watts, who was near tears during an interview, said he spent much of the night throwing up over the backlash. Lee Ielpi, whose firefighter son died in the attacks, said he understands the backlash from the ad, but he also believes it's important to remember 9/11. Ielpi, speaking in a telephone interview from the 9/11 memorial site, is president and co-founder of the 9/11 Tribute Center. "I think that any positive event is always beneficial to make sure we remember 9/11," Ielpi said. "I don't feel slighted by this golf outing." Watts also won support from golfers such as Colleen Savage, who said the whole thing was a misunderstanding. "I'm quite shocked," Savage said after playing nine holes on the course Tuesday. "I definitely think it's blown out of proportion." This is not the first time that promotions tied to 9/11 have drawn criticism. Last year the Coeur d'Alene Casino Resort Hotel in Worley, Idaho, offered hotel rooms for $91.11 and a food voucher for $9.11 as a "Thank you to our heroes." Two years ago New York Sports Club offered 9/11 first-responders cheap memberships, drawing outrage from some who were targeted for the discount who said it a shameless use of a national tragedy to make money. While offering a reduced price on Sept. 11 is more apt to offend someone than doing the same thing on Veterans Day, the Wisconsin golf club promotion could have been much worse, said Kathleen Culver, associate director of the Center for Journalism Ethics at the University of Wisconsin-Madison. "You have a small business that's woven into the community, they were doing a promotion, thought they were commemorating 9/11, they ran it and it blew back on them," Culver said. "They apologized. Really, does the story need to go any further?"