It is interesting to hear an explanation for superhero nonprevention of real-world catastrophes does exist (allowing real world issues to be addressed in comics).
As to the race thing and people's comments ... such folk are both infuriating and disgusting. And probably pointless to even converse with.
Though it would be interesting to see how any of 'em respond to this explanation for Storm's non-intervention regarding Katrina. If that was the explanation given in the X-Men comics for her failure to prevent such events worldwide, it is difficult to understand why "certain fans" would hold it against the character. We're are simply talkin' about a global dynamic in the imaginary comic book universe, that such a major positive regional intervention will have an equal and opposite negative effect someplace else. Now one might think this imaginary rule is silly, or maybe one doesn't, but it has NOTHING to do with the character of the character.
One problem with addressing "real world events" is Marvel's sliding timeline. Originally, heroes meet Kennedy, Regan and I think the Beetles showed up at Sue and Reeds wedding. But with the sliding time scale, all those events are negated out of continuity because they can't happen if the FF only went up about 7 to 10 years ago. WIthin a few years, REggie's Katrina storyline will either be negated or changed into an imaginary huricane.
So some writers would rather never touch real world, because it "dates" the story. (It's also the reason why some writers prefer made up slang, rather than real slang because it "dates" the book.) On the other hand, it's a fine line to have fictional heroes intervene without diminishing the real world's heroes' efforts. (for example, having Spider-man find the last survivor of the World Trade Center, would distort the real last survivor rescue.) This is probably one reason why Reggie has BP focus on fighting vampires rather than focusing on relief efforts.
Easiest answer to "where were the heroes?" They were busy being heroes elsewhere. Dr. Doom doesn't halt his plans because New Orleans flooded.