Fighting for a $15 per hour minimum wage: What would a Wholehearted Supporter do?

Let me preface this post with the acknowledgment that there is no easy answer to how to implement a city-wide minimum wage increase (which is the subject of local debate in Seattle). However, this complexity does not justify the heavy-handed language that some City leaders use to discuss the issue.

The mantra of some Seattle political, business, and other leaders who claim to be Wholehearted Supporters of a $15 per hour minimum wage: "There's a Right Way and a Wrong Way to achieve a $15 per hour minimum wage; to avoid Terrible Consequences, Seattleites should get behind the Right Way." 

Demanding that City Council pass a no-exceptions-$15-minimum-wage-in-2014 ordinance is Wrong; so is taking the issue to Seattle voters via a ballot initiative. Mayor Ed Murray worries a ballot initiative would "divide us." A co-chair of his minimum wage task force (charged with recommending how to implement a minimum wage) fears an initiative would mean a "financial bloodbath" for the business community and unions. Other Wholehearted Supporters warn that a no-exceptions minimum wage would destroy nonprofits dependent on low-paid staff and, hence, their services for low-income people; transform Seattle into a big-box store wasteland; suck the City of its soul; and more. 

What is the evidence for Supporters' claims; what considerations do their analyses ignore; and what is the effect of their public admonitions on workers, employers, and voters?