Free speech isn't a licence to kill.
Of course, it's good that a person be held accountable for their tweets and other communications. Neo-nazi or racist speech can be condemned, libel and false speech can be condemned. A person doing this can be outed as a bigot or liar.
But is that a reason for arresting a person? In the USA, the First Amendment to the Constitution says no. In other countries, apparently this is allowable, which is a dangerous tool in the hands of authorities.