Although I think they should have elaborated more on the catastrophe of the movie and Snow's radicalization and therefore perhaps split this film into two parts or even made it into a miniseries, I have to admit. This makes the original plot that much more enjoyable and Snow’s actions more understandable.
Katniss is literally singing the song Snow‘s ex girlfriend, who is also brunette and from twelve, wrote to spark a revolution against him. I would have been pissed too, if I were Snow.