I think that Deadpool can be a bit obnoxious sometimes, but that doesn't mean that teens 13 and up should not watch it.
I have watched rated R movies when I was 13 or 12 years old and I turned out fine. I was the same 13 or 12 year old I was before and after watching the movies. It doesn't bring out a bad influence for teenagers.
Technically teenagers are young adults and don't need to be bound down by their parents all the time, we have to admit they are not gonna be the same tiny little darlings we know and love forever, and they are not going to be perfect little children when you are not around. You see kids, everyday are disregarding the teachings of their parents when the parents aren't around, I see this everyday in high school. That's because they are in exploring and discovering new things, but that still doesn't change who they are.
They'll still be your children, and you can not protect them forever from the things that you see should not be presented to children. Deadpool actually brings out the humor that teenagers love. I laugh everytime I read a Deadpool comic, and l rarely find comic books funny at all. select your teenagers watch Deadpool, it's humor for the youth.