Doesn't BLM stand for Black Lives Matter, I'm sure we all agree, so if the official actually said 'that BLACK guy there' what's the issue. We have no idea about the colour of the other guys around him, so he could have just been differentiating to avoid confusion.
Seriously, could the official have said 'that non-white guy there'. That is nonsense (and he'd have got pelters for that too).
If the above is the case, it's getting a bit over the top now.
To think we got a bigger fine for being out on the pitch one minute late, than Porto got for their fans chucking bananas at Mario. UEFA will have problems dealing with this incident.