Two of UCSF’s most prominent financial backers have sent a clear message to opponents of the proposed Golden State Warriors arena at Mission Bay: Buzz off.

“The mayor and UCSF have put together an amazing plan that solves any theoretical potential traffic, access and parking issues,” Salesforce executive Marc Benioff — whose name graces the new UCSF Benioff Children’s Hospital at Mission Bay — wrote in an e-mail to the San Francisco Business Times on Thursday.

He was reacting to a press release by the Mission Bay Alliance — a newly formed nonprofit whose apparently well-heeled backers are keeping a very low profile — that charged that the Warriors are ignoring the traffic problems their 18,000-seat arena would cause and “are trying to sweep this serious parking problem under the carpet.”

“Marc Benioff tells the truth,” venture capitalist Ron Conway, one of Mayor Ed Lee’s biggest backers, chimed in.

Conway — who has given some $40 million for UCSF’s new campus and has his name on at least one building there — wrote in an e-mail that Lee “has worked tirelessly to cooperate with UCSF and the community and is well aware of the issues.”

Conway added that former UCSF Senior Vice Chancellor Bruce Spaulding, who is consulting with the group opposing the arena plan, and PR gun-for-hire Sam Singer are spreading “mistruths to confuse the public.”

The e-mails — which were cc’d to The Chronicle — make it clear that although some of UCSF’s benefactors are upset about the Warriors’ plans to move in next door, the feelings are far from unanimous. Of course, Benioff has a vested interest in seeing the deal go through — his Salesforce has agreed to sell 12 acres to the Warriors so the team can build an arena and a pair of 16-story office buildings.

“There is a fantastic opportunity for UCSF and the Warriors to work closely together in the use of the stadium, making office space available to UCSF, and joint marketing and branding as well,” he said.

Benioff, who gave $50 million to UCSF’s Children’s Hospital in Oakland a couple of weeks before the Warriors land sale was announced, called the new arena plan a “a win-win-win between the Warriors, UCSF and the citizens of the city.”

Singer told us he had already received a “nasty-gram” from Conway — for whom he’s done work in the past — asking him how he could be part of the arena opposition. “I told Ron we’re going to have to agree to disagree,” said Singer.

But he added, “When you have two of the biggest hitters like Benioff and Conway coming at you — you know you are doing the right thing.”

San Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Got a tip? Call (415) 777-8815, or e-mail matierandross@sfchronicle.com. Twitter: @matierandross