It's not only the left who impinge on academic freedom although they attempt to block campus speakers twice as often as the right.

Violence should not be used as a means to shut down discussion however some on the left, wrongly, think it is the only means to change.  Those on the right seldom see the need for violence because the current political agenda supports their philosophy.

On the other hand America has a president who encouraged violence at his campaign rallies and views it as an acceptable practice thus setting a bad example for all.