To an extent, I agree with Mally. If it was solely an anti-racism statement, then I think it would be less controversial, but it seems to be a direct support with BLM, which is what gets people's goat.
Having said that, the first game of the new NFL season featured the two teams joining together to support racial unity (not BLM directly). They were roundly booed by the (socially distanced) crowd. Whether it was a particularly idiotic crowd (I mean, who, extremists from both sides apart, doesn't want racial harmony or unity?), the fans not wanting to see the two "enemies" unite (the teams that is, not the races) or just sport starved fans just saying "get on with the football, I'm not sure.