In short, Democrats find out who funds free speech, or free market organizations or anyone who opposes their power grabs in policy and they threaten them with a smear campaign claiming that they are racist etc etc. 

Democrats actively provoke those who are mentally suggestable into acts of violence. 

This is why our libel and defamation laws need to be reformed. the Wall Street Journal’s Kim Strassel has details. This is very much worth your time.