What is the actual criticism? The Alt-Right is a hate movement. Twitter has a responsibility (both ethical and legal) to prevent their platform from being used to promote racism, sexism, Islamophobia, etc.
A single hashtag is in no way comparable to a fast growing white-supremacist hate movement which counts he President-Elect's right hand man (Steve Bannon) as a member.
So is #killallmen and multitude of others, yet somehow these tags still persist.