This is from Cal's official statement, that the cops thought it was too dangerous to hold the speech on campus next week, because they know that both sides would be coming to the speech with a taste for blood. Cal tried to accommodate it by making it only for students, during the day, and waiting until late notice to specify the location, but the cops still thought it was too dangerous. If you were a cop, what would you suggest, to hold the speech and put college students (most who don't give much of a shit and only want to get their degrees) and your officers in the line of fire between wackos in the fourth battle of Berkeley in the past 3 couple of months? Things are crazy right now, you can be quixotic or you can be practical and recognize that people are going to get hurt and property is going to be damaged over some stupid shit.
"Unfortunately, UCPD determined that, given currently active security threats, it is not possible to assure that the event could be held successfully -- or that the safety of Ms. Coulter, the event sponsors, audience, and bystanders could be adequately protected -- at any of the campus venues available on April 27th," the letter said.
"We realize that this is disappointing news, but the good news is that UCPD and Student Affairs remain firmly committed to working with you to find an alternative time and date for Ms. Coulter to come speak here at Berkeley. We expect most Mondays and Tuesdays in September during the day should work, though we will of course need to work through the details."
http://www.cnn.com/2017/04/19/us/ann-coulter-uc-berkeley/index.html