So when pictures surface of someone that the in crowd doesn't like is an old Halloween costume, they all play it up as if the person's a monster. Realistically, few if anyone actually care deep down, and so when the same thing happens to someone currently in favor, it's easy to let it slide.
The problem isn't that justin Trudeau (who I despise incidentally) got a pass for dressing up in a costume (which obviously wasn't remotely offensive in the context it was in), it's that other people's careers have been destroyed for the same thing.
Just like e.g. Bill Clinton "not inhaling" - nobody gives a shit if he smoked pot. But simultaneously thousands of people, mostly who are "undesirables" in the eyes of law enforcement for one reason or another get incarcerated for it.
Nah man that's just straight up blackface minstrel, extremely racist and bad. Sorry, you're confusing it with the other time he wore blackface.
Some folks were just too valuable to marginalize. Some aren't. But that's pretty true of any space humans operate in, whether the bad stuff is Halloween costume choices or bad hygiene.
If there are a hundred Justin Trudeaus to choose from, the one that was racist gets left by the wayside (I think this is what scares people about this sort of thing... They realize they aren't special enough to step out of line).
That "concern" in modern United States is literally the end of your professional life! So these self-appointed thought and speech police have, and will employ without a second-thought just for twitter points, through social media, a way to amplify their power to the extent that they can do something previously impossible and end your career over a (possibly imagined) thought "crime" or speech "crime". So from that perspective, all the walking on eggshells and concern about this is absolutely real not just a socially imagined construct or idea.