This is the hashtag:
Political disagreements are being "weaponized" by unscrupulous political operatives through the use of auto-posting bots on social media. They flood a hashtag, making it look like a lot of people don't like someone. That hashtag rises on the "Trending" charts. That fake consensus then tricks people into feeling more hostile than they otherwise would, and it lowers the barriers to spread hate, polluting connections real people have with each other.
In this case, it looks like there's a current botnet campaign that's trying to worsen whatever bad blood exists between Sanders and Warren supporters, similar to how Russian operatives created spambots that endlessly harassed Clinton (and Sanders) supporters during the 2015/2016 primary (the "Bernie Bros" pejorative was created in part by this--a 2017 analysis found that the most prolific pro-Bernie/anti-Clinton accounts on Twitter turned out to be Russian bots). When you see something enraging, take a moment to chill and ask whether the source and the message are real.
We need to remain skeptical of what we see on social media when it's something that gets our blood pumping about political opponents, whether that's a trending harassment hashtag or it's an article from a news source we haven't heard of before. If it sounds too horrible to be true, there's a good chance it's fake news created to divide us. Not always(!), but often.
There are good reasons not to agree (and even REALLY not like) someone in politics, and if we care about democratic rule we need to have a lot more conversations with each other about why do and don't support people running for office. But we need to be careful not to be taken advantage of by bad actors. Keep an open mind. And remain skeptical.