To take the knee? [I Believe In Freedom]

I notice we now have players in sport being threatened with death threats because they refused to ‘take the knee‘ to the BLM Movement. Which means there are certain people who are trying to take away our freedom of expression by violence. I am sure that most of us are totally against racism but why must we declare our support for a movement with which some of those values - such as violence- we are not happy with?