Nobody who works with kids would let them have a knife fight with real knives for example. Nobody is in favor of giving them the freedom to accidentally injure another child. Kids make mistakes with fire, guns, backyard wrestling, drugs, alcohol, and a host of other activities that responsible adults try very hard to prevent. We don't give kids unlimited freedom to make mistakes. Everyone believes in putting limits on freedom, we all just have a different idea of what an appropriate limit should be for the kids. If you have more rules than most people, you are called strict. If you are more permissive than most people, you are not.
I use Edmodo as a safe, private practice space for lessons about social media and I am faced with questions about freedom every lesson. The first question I usually get when I tell a group of 4th or 5th graders we are joining a social network is usually something like, "Can we use OMG and LOL?" I almost always say yes, but I try to help them see that if you write like you are a silly person, people will treat you like a silly person. If you write like you are intelligent, people will treat you with more respect.
Source: http://www.windows2universe.orgOther situations arise where the class might be writing a collaborative story and I have to make a judgement call about if something they write is funny or if it crosses the line. Sometimes the kids might write something that seems excessively violent or vulgar to me but explicitly limiting their freedom to write it will also dampen their creativity. I try not to directly address potentially inappropriate statements like "Hanna Montana should be the leader of Uranus" [real example] but repeat general guidelines like "ask yourself if you'd be proud to have your parents read the line before you click publish."
On one end, we want to encourage creativity and ownership of an assignment, on the other end we want to keep them from doing something they will regret. It isn't always easy to find the right balance point. I do believe it helps to hear how other people handle specific situations like these though, so if you have any tough calls to share, please let me know.