Same old mantra about NO, blah blah blah.
I lived for a number of years in N.O. and visit it often, usually a couple of times a year. Gang bangers on every corner is ridiculous, I was there last month and did not see any group of "bangers" in the Quarter, of course I am not hanging out in there at 3am after enjoying the night life. On the other I would not hang out in certain areas in any big city, Tampa, Houston, Fresno etc., use your common sense.
As for police presence you generally find more police where you find the most people, ergo police presence in the Quarter at night, that's where the people are. There is also a police substation there so again the noticeable presence of police.
To the OP you have apparently let one person's view change your mind but to others realize that NO is like any big city, and some not so big cities, there are area's you should avoid at any time of the day or night but realize this the French Quarter is NO's cash cow, they are not going to let the criminal element rule