It's such a tough piece that has so many layers to it once you really get into the debate. With so many of these mega stadiums being built with the idea that they will host other sports, concerts, etc and still be used for an NFL game 24 hours later you almost need the fake stuff to pull it off. Yeah you can do it with the grass, and yeah grass is probably safer in perfect conditions, but beat up natural grass becomes the worst case scenario too.
At least it isn't as bad as when a quarter of the league shared stadiums with MLB teams 30 years ago, that created some horrific conditions. Some of these teams in the north have some pretty beat up fields come December/January when nothing grows without a ton of work, and it shocks me that any of those teams have grass fields. Honestly I dont think there is a right answer here, I just hope the fake stuff becomes better and better quality over time.