Sayed Ahmed Alwadaei, of the Bahrain Institute for Rights and Democracy, says the Sheikh must not be voted as Sepp Blatter's successor because of human rights allegations.
The Asian Football Confederation president is the favorite to succeed Sepp Blatter as head of FIFA, ahead of rivals Gianni Infantino, Tokyo Sexwale, Jerome Champagne and Prince Ali bin al-Hussein.
But BIRD's director for advocacy has pleaded with FIFA to reject Sheikh Salman, 50, because of allegations that he was involved in identifying footballers involved in pro-democracy demonstrations in 2011.
"We are in Zurich today bringing the story of Bahrain's victims to the doors of FIFA," Sayed Ahmed Alwadaei told Goal. "At a time when FIFA should be reforming, it is on the cusp of destroying its remaining credibility. A victory for Sheikh Salman tomorrow is a loss for human rights. FIFA will be declaring its moral collapse."
Sheikh Salman's supporters and detractors gathered in Zurich ahead of the 207 member associations (Kuwait and Indonesia are suspended) casting their votes at FIFA's Extraordinary Congress.
Not everybody believes the member of Bahrain's royal family will drag FIFA into disrepute, with a group of around 50 supporters holding placards in favor of Sheikh Salman's bid for the presidency.
"Everyone has a different perspective of what happened, but we feel he is a clean man and he can make a difference for FIFA," businessman Mohamed Al Shaman, 25, told Reuters.
Sheikh Salman has repeatedly denied wrongdoing during the so-called Arab Spring five years ago, in which human rights groups have alleged pro-democracy demonstrators were imprisoned and tortured.
Last year, Human Rights Watch's gulf researcher Nicolas McGeehan commented: "If a member of Bahrain’s royal family is the cleanest pair of hands that FIFA can find, then the organization would appear to have the shallowest and least ethical pool of talent in world sport."
FIFA's reputation took a pummelling in 2015. Dozens of FBI indictments, World Cup bid bribery allegations and its own president Blatter being banned from the sport for eight years — since reduced to six — left many questioning its claims that it was committed to cracking down on corruption.
The world football governing body has, however, passed structural reforms which, if implemented, will increase independent oversight in the upper echelons of the sport.