Salesforce CEO Marc Benioff. Mike Windle/Getty Images for Weinstein Carnegie Philanthropic Group Salesforce CEO Marc Benioff isn't happy about the prospects of filmmaker George Lucas opening his own museum in San Francisco — a plan that was rejected two years ago by the city.

In a series of tweets on Monday, Benioff voiced his opposition to San Francisco Mayor Ed Lee's lobbying campaign to bring back the rights to build Lucas' museum to the city. The filmmaker wants a place to exhibit his popular-art collection.

After failing to get the approval in San Francisco in 2014, Lucas has been working with Chicago city officials to build his own museum there, although the plan has recently hit a roadblock following a lawsuit.

Now Lucas and Lee have held talks about putting the museum on San Francisco's Treasure Island, according to the San Francisco Chronicle. But that's already raising some opposition.

"SF @sfgov & @mayoredlee should only support Lucas Museum if George Lucas does something for SF Schools, Hospitals, & Homeless," Benioff tweeted.

The tweets seem to raise concerns around the additional cost and tax breaks the city of San Francisco would accrue as a result of supporting Lucas' museum.

According to The Wall Street Journal, Lucas' proposed museum in Chicago would cost $1.2 billion, of which Lucas pledged to pay roughly $700 million. The rest would have to be paid off by the city, which is one of the reasons why Lucas' museum still hasn't been approved for construction in Chicago.

Salesforce declined to comment.

Benioff's tweets against Lucas and Lee are the latest in the billionaire CEO's many acts of social activism.

He's recently helped reverse a couple of "antigay" laws in the states of Georgia and Indiana by threatening to reduce investments in the regions. He's also known for rallying other CEOs to join his cause in order to win more public support, earning the nickname "corporate bully" from certain lawmakers.

Here are Benioff's tweets in response to Lee and Lucas:

—Normal Josh Kelly (@jcoltkelly) May 16, 2016