Changing your repo to Main from Master is probably the least useful thing you could possible do to fight modern slavery or to fight racism or to do anything but virtue signal to your co-workers.

You are not being kind you are belittling and making a real event that hurt many into a silly game. Racism and slavery are real things you and your co-workers can fight against them if you truly care.

Get in touch with the oldest org fighting slavery: https://www.antislavery.org

They could use your money, time and network. The one thing they don't care about is changing master to main in your github repos