Sale winger Marland Yarde says some of his team-mates have received death threats for the way they have responded to the Black Lives Matter movement.
All of the Sharks players wore 'Rugby Against Racism' T-shirts before facing Exeter on Friday, and five took a knee.
Sale's South African players did not kneel - and have been criticised by the country's sports minister.
Premiership Rugby has allowed clubs and players decide their own ways of supporting the campaign.
"I stand 100% for the Black Lives Matter movement and wholeheartedly believe in the importance of highlighting the continuous battle that we face in society everyday and the need for a change," former England winger Yarde posted on social media.
"I have to also stand against death threats against my team-mates which is totally unacceptable. This behaviour will not make the world a better place."
While almost all players from some teams have knelt before games, others have had a mixture of players kneeling and standing respectfully.
Saracens' England forward Billy Vunipola said he did not take the knee before his side's game with Bristol last week because of his Christian faith.
In football's Premier League all players and officials took a knee before the start of every game after the season restarted, while both England and West Indies cricket teams did so throughout their recent Test series.