I will admit that there is a lot of staged violence in the show, and Hannibal doesn't go more than a few minutes without sticking a cigar in his mouth, but there are lots of good messages in the show (e.g. sticking together, seeking police help, making good choices, it's never too late to turn your life around). The fighting might be hard for younger viewers to figure out (i.e. why it's okay for some people to fight but not others).
In an age where sex is used freely to promote shows for tweens (and sometimes, even younger), this is a classic in our house. I can let the kids watch this show unattended or watch it with them, and not be embarrassed by the content. I highly recommend it.