In the UK, these left-wing hashtags barely surpass 3,000 if even that. When you think about how much of the population actually uses Twitter, that ain't shit. And then, you have to take into account how many of these tweets are people condemning the movement. The amount the supporters of these movements are often a minority (Blacks and Jews, and even fewer Whites), just with much higher platforms.

EDIT: Plus, Twitter is more than likely forcing these Trends to the frontpage.