Maybe Donald Glover isn't the perfect actor to play Spidey, but saying a black actor couldn't play the part and play it well is downright racist.
No, no it really isn't.
Not if isn't about intrinsic acting ability, anyway. I mean, I grant you that saying "Black actors can't play roles as well as white actors," yeah, that's racist. But saying, "A black actor can't play Peter Parker" isn't racist at all. It's just saying who the character is and who can effectively play the character. It's no more racist than saying "Peter Parker is white." That's not a racist statement. It's a statement of fact. No comic book character "transcends" race, ok? And it's not like we're dealing with material as fungible and as intentionally manipulated as Shakespeare, where any number of people could end up playing the parts.
This gets at what makes a character a character. Is it there personality traits? Their abilities? Or is it more? Could you cast an Arabic Harry Potter? I don't think so. How about a Haitian Superman? Nope, don't think so either. Why is that? Simple. Because that's not who those characters are. None of this is to suggest that Haitian or Arabic actors are any less talented than white actors. I wouldn't cast a white actor in the role of Black Panther. Nor would I cast a white actor in the role of Mariko in some future Wolverine project. Not because white actors are incompetent or whatever, but just because they probably aren't right for the role unless they don heavy makeup, and even then, it's still kinda off.
These characters come from comic books -- an inherently visual art form. The more you deviate from the original version of the character, the more you lose of that character. With ancillary characters it's LESS of a problem, but it's still a problem. I thought Michael Clarke Duncan was fine as the Kingpin, but to me the Daredevil roles aren't the REAL Daredevil story. But bear in mind, I had just as much problem with Duncan playing the Kingpin as I did with Collin Farrel playing a raving lunatic with a bullseye carved into his forehead as Bullseye. That's not who either character is, and both are major deviations from the original material. Are they critical flaws? That's debatable. I'd say not quite, but they're enough to make me consider them to not actually be the "official" representation of those characters. Partially because the movie sucked, but also because they just didn't look right. I might be more forgiving if the movie kicked ass, the way I was about a black Nick Fury in Iron Man. Not because I have a problem with Sam Jackson (although I've not seen him stretch himself as an actor in a while....but then again, I did really try to avoid The Spirit), but just because, to me, Nick Fury is a white dude who chomps a cigar and is a WWII vet. So, Sam Jackson's performance is fine in a good movie, but I still think of him as "Nick Fury, but not the real Nick Fury."
This gets especially difficult when you deal with the main heroes of a story. Morgan Freeman is an amazing actor, but I wouldn't cast him as Professor X. Nor, for that matter, would I cast Edward Norton (setting aside his appearance as Bruce Banner), nor would I cast a younger Alec Guinness. These are all highly talented actors....who are also WRONG for the part.
You're dealing with comic book characters, ergo your actors have to not only be capable actors in general, but they also have to look the part. I thought the notion that Liev Schreiber -- an actor whose work I genuinely respect and enjoy -- could play Sabretooth was friggin' asinine. Why? Because he's WRONG for the role. He doesn't look a thing like Sabretooth no matter how good of an actor he is, no matter how many pounds he puts on. If they'd put him in a ton of makeup and a blonde wig, ok, maybe. Big maybe. But they didn't even bother and he just...looks...wrong. Not like the character. Not at all.
So, spare me the "That's racist!" rhetoric, ok? It's not racist to say that an actor doesn't look the part any more than it is to say that the character itself is of a particular race. Spiderman is white, ok? So's Superman. So's Captain America. So's Thor. Black Panther is black. Jubilee is asian. Dawnstar is native american. Sunspot is brazilian. That's who these characters are and it isn't racist to say so. To say otherwise is just asinine. You might as well call a dog a duck and a duck a Sherman tank. Wait, I'm sorry. That's tankist.