Sale wing Marland Yarde says some of his team-mates have received death threats relating to how they have marked the Black Lives Matter movement.
The club's South African players have been criticised by their country's sports minister, Nathi Mthethwa, for opting not to take a knee ahead of Gallagher Premiership matches against Harlequins and Exeter.
Sharks players had appeared in anti-racism t-shirts before both games.
England international Yarde, who was among a handful of Sale players to take a knee on both occasions, branded the threats "totally unacceptable".
"I stand 100% for the Black Lives Matter movement and whole heartedly believe in the importance of highlighting the continuous battle that we face in society everyday and the need for a change," the 28-year-old posted on Instagram and Twitter.
"I have to also stand against death threats against my teammates which is totally unacceptable. This behaviour will not make the world a better place. We are united we are a team."
Only four of Sale's starting XV took a knee at the Quins match on August 14, with five players doing so ahead of the clash with league leaders Exeter a week later.
In the aftermath of the Harlequins match, Sale director of rugby Steve Diamond said: "I think it'll be a storm in a tea cup.
"We all wore the rugby against racism T-shirts, which we thought was important, but I don't think it's too much to worry about if I'm honest."
England forward Billy Vunipola said he did not take the knee before Saracens' game with Bristol last week because of his Christian faith.
The PA news agency has contacted Sale for comment.