(or she)
The current Robin is kind of an elitist jerk, but kind of difficult to tell if this transcends to racism.
Who do you think might be racist in private in the super hero universe?
Hitler Man.
You bastard! Ha, I laughed out loud. Too funny.
Dynamic Man…not only plausible, but canonically true.
Some that haven’t been shown to be explicitly, but could definitely have the personality.
Punisher.
Ultimate Captain America (as opposed to the main universe version, who is anything but).
Mmm…that’s all I can think of.
And, no, Damien’s not racist, at all - sexist, yes, racist, no.
The Comedian is a pretty safe bet, off the clock or on. He also strikes me as the sort who’d drug test welfare recipients with a turkey baster.
Of the universally-known ones, I’m thinking Superman - he’s the only one AFAIK who was raised outside a big city (or the surprisingly racially-diverse Themyscira) - whereas Supes was raised in the rural Midwest, not exactly a hotbed of racial diversity. Plus all the Kryptonians I ever recall seeing are White.
Other points - Original Supes was (again, AFAIK) surrounded by a White supporting cast, whereas Bats went so far as to have a non-White girlfriend, Hal Jordan’s best friend was an Inuit, Ditto Tony Stark’s best bud Rhodey was always black, and Spidey’s a liberal college grad 
OTOH, it seems Supes isn’t totally averse to having a Black girlfriend, either…as long as he doesn’t have to marry her (man, I wish I could read that whole comic)
Barry Allen. Let’s start with the buzzcut.
Also Guy Gardener.
Captain America, Wolverine, any other supe with limited or total immortality.
Unless they have made concerted efforts to question everything they have ever learned and even their basic personality it is pretty much a given that they have outdated and to modern sensibilities offensive opinions about different races, religions and atheists, sexuality, women, the list goes on and on.
They could have been super progressive in their own time, that won’t help them now. The politically correct view is always in flux and things that seem outrageous to modern views were politically correct in their own time(there was a time when Marcus Garvey agreed with “send blacks back to Africa” racists).
If you want just a taste of this watch the film Look Who Is Coming To Dinner and remember the father is specifically stated to be a civil rights crusader. Imagine that at the time the film was made even a supporter of the civil rights movement was uneasy about his daughter marrying a brilliant black physician just because he is black.
His sidekick, Aryan Boy, wasn’t the most welcome dinner guest either.
I guess Wolverine’s attitudes gets “reset” with the various memory issues he’s had, though.
But Cap is definitely written as a 40’s relict - esp. in the Ultimates, it comes out in his relationship with Wasp. But she is Asian in that…
Lobo, if you consider him a hero. I agree that The Comedian fits the bill.
Have a look at Hate Monger (although he’s a villain. He got killed in his first appearance, but still managed to show up later on)
I didn’t know about that one - although radio Supes is a completely different animal, you’ll note I didn’t reference the Smallville continuity, where Supe’s best man friend is Black.
Superman has also, for personal reasons, always been very senstitve to the plight of immigrants in the US.
We’re talking about the guy who handpicked a black dude as his replacement in the Avengers back in the '60s – before spending the '70s hanging out in Harlem with Sam Wilson, before spending the '80s dating a nice Jewish girl who was studying to be a lawyer? I think we’ve got decades of evidence that he ain’t exactly the guy in the Ultimates.