Make people accountable for spreading lies and missinformation. Its that simple. The more reach they have, the higher the punishment for spreading miss information.

And in order to make it easy for everyone, if you can proof that you did a research before publishing said missinformation it can lower the punishment. Again, more influence, more research necessary.

If we could start using block chains for information spreading, we could follow the sources of said information and everything would be tranparent.