Bayern Munich have defended Hoffenheim owner Dietmar Hopp after Borussia Dortmund supporters displayed a banner depicting him in crosshairs during their match at Hoffenheim on Saturday.
Hoffenheim said in an open letter that the banner was "incitement to murder."
The relationship between some Dortmund supporters and their rivals has been strained since Hoffenheim were promoted to the Bundesliga in 2008 with the help of billionaire Hopp.
They believe Hoffenheim's arrival opened the door to the undermining of the Bundesliga's football culture by working around the 50+1 rule, which stipulates that more than 50 percent of a club must be owned by members.
Bayern have business ties with SAP, the software company Hopp co-founded in 1972, and in a statement president Uli Hoeness and CEO Karl-Heinz Rummenigge said they "strongly condemned the shameless chants and banners against this man of honour."
"The outrageous and uncalled-for hostilities against Dietmar Hopp in German stadiums reached a shattering climax at the weekend," a statement read.
It said "football must declare its solidarity against such aggression" and added that it would be "fatal if people like Dietmar Hopp were to one day leave sport."
"This would be a devastating signal and moreover a big damage to football and especially for youth teams," the statement added.
Dortmund CEO Hans-Joachim Watzke has apologised for the banner, which was displayed after banning orders were sent to 33 fans who had insulted 78-year-old Hopp during the final match of last season at Hoffenheim.
"[Hopp] no longer brings his grandchildren. He only feels ashamed. To see that is unbelievable," Christoph Schickhardt, a lawyer for Hoffenheim and Hopp, told Sport1.
"It [the banner] is a new dimension. Crosshairs mean you want a targeted shot on someone before you kill him."
Schickhardt said he was "personally concerned about Dietmar Hopp's security" and added that games should be called off if something similar happened again.
The German FA (DFB) has opened proceedings against both Hoffenheim -- on suspicion of insufficient security -- and Dortmund in the wake of Saturday's events.
SAP has partnerships with the DFB, Hoffenheim, Bayern and the City Football Group, among others and has cooperated with Bayern since 2014.
Earlier this month, it secured the naming rights for Munich's new multifunctional arena which will be built by Red Bull, whose hockey team Red Bull Munich will play there alongside Bayern's basketball team.