There are people who will organize and train people to infiltrate and promulgate propaganda through social media sites.
Sometimes you’ll see obnoxious, hate filled crap posted by someone to try to tie a certain behavior to a political or ideological enemy.
Indeed. Look at the robocalls that were made accusing McDaniel and his supporters of racism. Paying people to post to a website or post comments to news stories isn't too far removed from paying them to make phone calls.