Bay Area civil rights advocates on Monday called for a boycott of the San Francisco Giants, citing billionaire owner Charles B. Johnson’s contributions to two political campaigns that have come under fire for racist statements.

Johnson and his wife, Ann, donated a combined $5,400 to the campaign of Senator Cindy Hyde-Smith, an incumbent Republican in Mississippi who is up for re-election Tuesday. In recent weeks, the senator has been marred in controversy over remarks she made at a Nov. 2 campaign rally regarding a local rancher.

“If he invited me to a public hanging, I’d be on the front row,” Hyde-Smith said.

The Johnsons’ campaign contributions were received nearly three weeks after that comment was made.

In a statement Monday, John Burris, a prominent civil rights attorney in Oakland, urged fans not to attend Giants games “as long as Charles Johnson is associated with the team.”

“This is outrageous, hurtful conduct not only to me philosophically, but certainly to people who live there that they could be subjected to that kind of violence,” Burris added. “It could suggest in many ways that their citizenship rights are going to be undermined by the politics of that situation and racial bias.”

Johnson is one of the biggest stakeholders in the Giants, if not the biggest.

The team released a statement late Monday morning condemning racism and hate speech, but noting that the Giants have no influence over its 30-plus owners’ political beliefs.

“Neither I nor anyone else at the Giants can control who any of our owners support politically, just as we cannot and should not control whom any of our employees support politically,” team President & CEO Larry Baer said in a statement.

Burris, who was scheduled to hold a press conference Monday with Dr. Amos Brown of the National Association for the Advancement of Colored People, noted that Hyde-Smith’s comments and Johnson’s financial support are particularly hurtful given Mississippi’s history of voter suppression and racial violence.

“This is an issue that’s far greater than supporting a baseball team,” Burris said. “(It’s) where the owner’s values are totally inconsistent of this entire community and contemporary modern views of the social order.”

Johnson, a retired billionaire who started the investment firm Franklin Templeton Investments, also came under fire last month for donating to Black Americans for the President’s Agenda, a super PAC that released a racist attack ad in Arkansas. The radio commercial featured two women saying Democrats could bring back lynchings if black voters didn’t support a Republican candidate.

Johnson withdrew his support from the super PAC after the ads aired and released a statement in October condemning “any form of racism.” He claimed that he had no knowledge the funding would be used for such an advertisement. The goal for a boycott, Burris said, is to pressure Johnson to either relinquish his connections with the Giants or at least withdraw his support for Hyde-Smith.

Hyde-Smith has also drawn outrage for a photo posted to Facebook in 2014 in which she wears a Confederate hat, as well as a video of the senator saying it may be “a good idea” to make it harder for college students to vote.

Other civil rights leaders, such as Dr. Harry Edwards, a professor emeritus of sociology at UC Berkeley, have expressed support for the boycott on social media.

Several corporations, such as Walmart, AT&T and MLB, have requested the return of contributions made to Hyde-Smith’s campaign before her remarks became public.

Gwendolyn Wu is a San Francisco Chronicle staff writer. Email: gwendolyn.wu@sfchronicle.com Twitter: @gwendolynawu