Yeah, now that everybody saw MP stretching in Prague before he started to FS, freestylers are realizing that it maybe isn't such a bad idea, lol.
No wonder there are so many freestylers with chronic pain/injuries, when most of them aren't doing anything even remotely similar to warming up or stretching after training and are exposing their bodies to hard training for a long period of time.
Long story short: warm up & stretch (mostly dynamic with some static stretches) before training and stretch (static) after it. When you have an injury, TREAT IT, don't be a smartass and try to work through it. Also, myofascial release is a great way to remove already existing scar tissue and work on tight muscles.