That's why leftists breaking windows is far more alarming and worthy of a lot more spilled ink than alt-righters murdering Muslims and black Christians in their places of worship. Leftists represent a disruption in the balance of power, while right-wing extremists represent a minor glitch in the system working as intended. Bashing a Starbucks window in carries far more resonance to middle class types who want to preserve their comfortable life above all else, than piles of dead minorities.
This is an easy caricature that I doubt applies to many, if any, of the people wringing their hands about free speech issues. It gives you ample grounds for moral contempt, but I don't think it's either accurate or useful.
The reason they're not more upset about the lunatic in Canada and Dylann Roof is that such event are (thankfully) rare. No one is whistling on his way to work as he passes "piles of dead minorities" every day.
Ironically, it's precisely the same reason that Trump's refugee nonsense is so stupid - yes, some minuscule percentage of refugees might be terrorists, but terrorist attacks in the US, from Muslim refugees or others, are *rare*. They are simply not the problem that the xenophobes make them out to be.
On the other hand, public views on free speech issues and the appropriate uses of political violence -- and the widening chasm between liberals and conservatives in the US -- could be immensely consequential.
I say all of that as a person who doesn't think that Berkeley should have given this asshole a platform in the first place. Uncomfortable speech is one thing; attempting to ruin the lives of specific students is another, and it would seem well within the university's purview to defend those students from that sort of attack.