The "goofy advertising characters" were racist. In the same way that "spanking a wife" for buying the wrong brand was considered "funny". Those adds worked because they were aimed at a racist/sexist public. Those adds weren't funny to the people the supposedly "goofy characters" represented.

The costume is salt on the wound. And the same way that the adds where a husband spanked his wife normalized the real spanking, the "goofy characters" normalized consider the people that they represent as "simple" or "dumb" and affected how they were perceived (which affect wages and jobs). So what for you was "harmless fun", might have translated to being treated like shit for the ones mocked.

While I do believe that firing people for things done decades ago is not the way to go, I do also think that saying "back in the past it was OK" is not an aceptable answer. If indeed those colleagues are not racist, they should feel ashamed of themselves. Because they did wrong even if they wasn't their intention.

And in the same way that you think that those mistakes don't undone the good things they did, the good things don't undone the bad ones. It is fair that we hold people accountable and while I don't ask for people being fired, asking for that people to acknowledge their wrongdoing is the first step. After all, one of the common arguments that are used to not stop doing something wrong is to say that "it always has been that way and no one complained!".

So yes, people have a right to complain about those things. It is a way to stop them today. After all, one of the reasons that now people don't use that kind of costumes is that now there are consequences.

The point is that people don't want to be the butt of your jokes. It is telling that there are no "goofy characters" based on "White men".