It is also intellectually sloppy, to an extent that discredits its author. One of the lessons I learned after I graduated from Berkeley is that unaired prejudices tend to fester and can, one day, burst in ugly ways. The war in Bosnia, which I covered, is a case in point. Much of the nationalist fury in the Balkans, especially on the Serb side, stemmed from the manipulation of grudges that were not allowed to surface during Tito's long rule. Nothing was proved or disproved, and as a result, terrifying wars were fought on the basis of myths.
Enforced silence is an inadequate defense against prejudice and discord.
A better strategy is to let everyone say what they think in a civil way. To be sure, Horowitz's ad wasn't especially civil, and the paper might have requested that he tone down his incendiary language. But by letting people air controversial views you at least discover who and what you're up against, and can begin to figure out a way to bring the truth to those who need it. All of which makes the ongoing controversy around the Daily Cal a positive event. Just beware of the beer ads.