If the tourists in question were lodged and sheltered, then they were already a step ahead of those they were evacuated out ahead of.
Now, I'm not going to question this any further. It may be that these tourists had other factors requiring their evacuation. It is likely that their rooms in the hotel required for rescue and recovery purposes. In that particular case, I agree that just evicting them to fend for themselves would've been a bad idea, and unfair.
There was another group of tourists to which this had happened. They'd made private post-disaster evacuation arrangements and their buses were confiscated. They were unfortunately left to fend for themselves after having been evicted from their hotel, left without their transportation, and none of them were supplied with information or the basic necessities.
Classism would apply if there had been no pressing need to evacuate those tourists. They were already provided with shelter, toss them some food and water, and evacuate those with the most apparent need first.
Of course, we'll never have all the information here. It was nothing more than a passing mention as far as totoal coverage of the disaster goes. It is possible the mayor's motives were suspect, but not very likely. In a chaotic situation like NO, a lot of decisions are going to have to be made quickly with imperfect information.
You are welcome to suspect anything, but taking care of strangers is one of the staples in Judeo-Christian morality. This "rule of thumb" exists in part because they are KNOWN to suffer more in a typical situation, and nobody in crisis has time to evaluate the suffering with precision that you suggest.
Though shall care for the widows and orphans in your midst, and for the strangers, for you too were a stranger in the Land of Egypt.
Observe that these people spoke English. What is a foreigner to do if (s)he does not.
I don't know whether you travelled much, but I do hope that you will be treated better than what you advocate yourself.