What are pros and cons of propaganda

There's not really any pros for propaganda because essentially what you are doing is lying to get someone to believe something. I guess you could say a pro is that gullible people will believe you, but that's an unethical pro. The cons are that it usually causes much controversy in a society where there's not supposed to be a bias in the government. Propaganda in its true form is never a good thing. It is unethical in the sense that it takes advantage of people who are too lazy to do research and quick to believe what someone tells them. One example I like to use is many of these independent "news" websites. On both ends of the political spectrum, left and right, you find websites that have articles so heavily weighed down with that wings propaganda that true news becomes less and less visible. Occupy Democrats is one textbook example of that. Their articles are so left leaning that you read an article and are immediately left with a left leaning impression. Same goes for a lot of right wing websites. I'm not going to say "always" but propaganda 99.9 percent of the time is not good. Instead of people doing their own research to decide their view on something, propaganda tells people what they should think versus the asking people what they think

 The pros are manipulation of the public and eyes on. 
The cons are the destructive outcome to the public.

Both the han and the roman empire decline as a result of social unrest during their collapse.