For me, an issue here is that of the stark either/or opposition. EITHER you openly support #BLM, and make easily recognizable gestures which show everyone else that support it, OR you're racist. I want to broaden that discussion beyond football: football is one context in which there's a well-documented and longstanding problem with racism. It needs to tackling at every level, although I do think there's mileage in the suggestion that if it becomes an established ritual at the start of every game, it will lose impetus.
But the Either/Or divide isn't that simple. As a PP pointed out, you can believe black lives matter and still be deeply uncomfortable with #BLM as a movement, its funding, its occasional misappropriation, and (for me at least) its place in a broader, censorious culture in which not taking the knee, or not wearing a poppy, or not announcing your pronouns in accordance with whichever ideology demands it, can and has resulted in people being threatened, intimidated, and even in the loss of their livelihoods.
I'm uncomfortable with #BlackLivesMatter as a movement for these reasons. I'm uncomfortable that even a discussion of these reasons is shot down with cries of 'racism'. I'm similarly uncomfortable with the 'all lives matter' mantra. I'm white. I've never in my life experienced discrimination, abuse, ridicule or been attacked because of my skin colour. I've never tried to trace back my ancestry and found it stops at a particular point, because this was the time of the slave trade. To acknowledge that deeply painful history is not to be a self-flagellating apologist, as some on this thread have suggested. White privilege exists, just as surely as male privilege does. If you have it, you can't necessarily see it, but this is why so-called 'colour blindness' is a particular problem.
For me, a key problem is a lack of critical engagement with these issues. In some situations, the cost of discussing them is too great: it only takes one comment to be misconstrued and real consequences can ensue. So people stay quiet and fester, but their real views sometimes come out in threads such as this. We've learned in recent years that the kind of misogyny viewed as antediluvian back in the noughties was never simmering too far below the surface, but in recent years has come back with a vengeance. The same thing seems to be happening with racism.
I think it's vital these discussions continue, albeit they are so difficult and uncomfortable.