A person cannot choose to change the points or opinions of their friends, they have the choice of accepting the differences that they have or finding new friends, since a person is unlikely to find people of exactly equal moral standing they must either socialise with people who will change their opinion or omit other people from their lives, being social creatures (hence the ease with which people form communities and the abundance of towns and cities around the world), people are much more likely to choose the former option. If you disagree with a piece of media, you choose a different game, change the channel or switch it off and hang out with your mates.
Media can be fairly effective at changing your opinions of things. I have seen many unthinking drones follow whatever their news station spits out to them, hardly holding a valid opinion of their own. But personality deals with people, and people have the biggest effect on our personal lives. We are social animals above everything, and will flock like seagulls to do whatever our friends are doing, preserving the traditional social hierarchies of the tribes. But as more and more people get disconnected from reality through technology, maybe the trend will reverse in favor of media.
Mass media plays the greater role because it can bypass the critical factor which is needed to influence people's personality and social outlook. People are limited to their own experiences, whereas media has a greater range of desirable ideologies. Groups are equally influenced between the members whereas Media is one sided. And Media is considered to generally be the more reliable source. (follow the Debate between Josh_B and Brepar.)