Football

Dude, if you were as sensitive to this as you are to every time someone makes out all scousers are thieves, or dodgy as fuck, then you might be able to get your head around it.
But since you won't make that connection and scouser's aren't systematically demonised, jailed, and/or killed for having an annoying accent rather than the colour of their skin, you can still get on your high horse about it, and hold your hands up like, "what's there to be offended about".
If I were being sensitive I would say you're just as unconsciously racist as Griezmann, and anyone else who decides to black up, and then gets upset when people call you on it, because you know "it's all just a bit of fun, where's the harm in that".
As a white male, who gets the benefit of 300 yrs of racism, you don't get to tell anyone whose dark of skin, what they can or can't be offended by when it comes to race. Because you know that's kinda fucking racist as well.

He could have dressed as a Globetrotter without reference to race. White guys jump too.

Pistanator

I don’t get the fuss. He’s dressed up as Harlem Globetrotter(I believe?)

Why is it racist or offensive?

Whilst the history of clowns goes back hundreds, possibly thousands of years, the 1800's depiction of black slaves and the birth of savage racial stereotypes which still stick today has meant this is still shaky ground. Dressing up doesn't necessarily equal a hate crime but when you still have white kids in the US that dress up as the murdered child Trayvon Martin for fancy dress ['cos laughing at the death of a child is a big fucking laugh] it's not hard to see why most choose to steer clear of the subject matter.

What is interesting to note in the link is how the not a single term was created by blacks including the N word...So when folk ask how come I can't say it, you can remind who created the term in the first place.