Personally, I don't think we have to struggle too hard. The evil in question has to do with xenophobia and religious hatred, both of which can be stirred up or damped down by political leaders.
On the negative side, you've got the example of a Slobodan Milosevic, whose thirst for power caused him to fan the flames of Serbian Islamophobia into genocidal rage. On the positive, you've got the example of a George W. Bush, who in the wake of the 9/11 attacks insisted that Islam was not the enemy.
To be fair, in Gov. Walker's statement he does go on to refer indirectly to those targeted by white supremacist Wade Michael Page as "our neighbors and friends." Still, I think Silk is right: more Republican leaders need to join John McCain in going out of their way to speak out against religious bigotry and to speak well of religious minorities. As president, Bush did this repeatedly (something the left has tended to forget, lest it stand in the way of framing the guy as history's biggest monster). Now this falls to Walker, Romney and others.
President Obama: "We are reminded how much our country has been enriched by Sikhs, who are a part of our broader American family."
Milwaukee County Executive Chris Abele: "Residents of Milwaukee County have an amazing ability to support one another in times of crisis. This is one of those times. The Sikh community is an important part of what makes that happen in Milwaukee County, with a long tradition of standing up for and supporting others. Now we need to stand with them."
Milwaukee Mayor Tom Barrett: "The Milwaukee region values its reputation as a region rich with diversity, and the Sikh community of southeastern Wisconsin is an important and positive part of that."
U.S. Rep. and U.S. Senate candidate Tammy Baldwin: "We stand by members of the Sikh community, who have given so much to our state."