Rumors aren't spread by bots, they're started by bots and spread by humans. The more outrageous the bot-rumor, the faster and voluminous it spreads. And the spread increases further when it gets reinterpreted and E-mailed or tweeted around.
People start rumors, half-truths and untruths, too. I'm not a Twitter follower, but the few tweets I've seen posted here and there, or forwarded, which were controversial or talked about had their origin in a tweet by an actual person, with an actual face or name, usually and actual title, and the tweets were written in real English, almost always by an American.
The only 'bots' I have actually seen were FB posters who -- when you looked up their profile -- had just signed up a few days previous, had a generic Anglo name, and usually were born in one major US city and lives in another major US city but they have no job title, no information, and few, if any friends. Sometimes their English is marginal, other times it's more like textese.
Sometimes they have no picture, and if they have a picture, it looks like it was cut and pasted from an advertisement or stock modeling photo, or stolen from another FB profile. In other words, the political version of the female, social media 'bot' data harvester.