Does life really imitate art?

It’s been said by many people on many occasions that violence in films leads to violent acts being committed in real life. To be honest this idea has never entirely sat comfortably with me. If we exclude children, who are generally more susceptible to imitating behaviour they see and in the eyes of the law should not be watching films above their age anyway, then why would a film change someone’s personality? Say a causation man named Fred in his mid 30’s, wife, two kids, works for a bank and drives a family car, decides one day to go into his local to support his football team with some friends. What are the chances he will start a fight with football fans from an opposing team, just because he has seen it in a film? This, to me, makes as much sense as if I were to decide, after 22years of thinking marmite is revolting, that because I like Paddington bear and have seen the new marmite adverts with him in I must now eat it. I have never been inclined to stuff my face with marmite sandwiches, and therefore the suggestion of it on television does not change my stance. Surely the situation with Fred is the same? Unless he has the inclination to start a fight, watching a film would have no effect in his behaviour at all? As long as a film does not contain anything illegal, is age appropriate and the viewer is aware of what it contains from the outset, why do we even need them to be censored? Surely the fact that there are people creating the film in the first place would imply there is some sort of demand for it? If so, who are we to stop it?