The best place to start is for moderate Muslims to come out en masse and denounce this kind of thing when it happens anywhere in the world. Right now the extremist have the loudest voice, and that causes the knee-jerk reactions we see.
The problem is two-fold in my opinion. First, the press tends to report big stuff like this when it happens with equal coverage of the moderate community denouncing this as an aberration of the Islamic faith. In fact, they should give more coverage to the moderate voices. Stop plastering images of the attackers and beheadings and burning embassy's all over the place and start coverage on the moderate factions that make up the larger community that need a voice.
Second, and one I think needs to be equally addressed, is the moderates that are not actually speaking out against it. While more will come out against something like this happening, others will be silent on the treatment of women and homosexuals in the larger Muslim community. It is past time we have an honest discourse with the tenets of the faith itself, and the issues that arise from it. In a place like Iran or Saudi where homosexuals are at best treated like second-class citizens, and at worst executed, there really isn't a honest leg to stand on when condemning something like this incident. That needs to be addressed. Ideas and beliefs have consequences, and we need to be able to question these in an honest manner without being labeled "Islamaphobic" by the liberal side of the debate. Its hard for me to believe that this shooter would have done what he did without harboring some ideas about the place homosexuals have in God's plan.
Reform needs to happen from within the faith itself and honest debate from outside the faith.