It's become a campaign against all kinds of discrimination, injustice, etc.
It also includes homophobia, LGBT, womens rights, etc.
Mark Bullingham, FA CEO said:
“We stand firmly against all forms of prejudice, so a key pillar of our strategy is to use our influence to deliver a game free from discrimination. We are striving to ensure that football at all levels is a safe environment for all, embracing diversity and inclusion, whilst challenging hateful conduct both on and off the pitch.
“We are very clear on what this symbolic gesture originally stood for 200 years ago and what it continues to stand for today, and that is a fight against injustice, inequality and discrimination. We will support any players who wish to take a stand against racism and discrimination by taking a knee. They have our unequivocal support.”