A lot of people see still see diversity as a Nice to Have, rather than something that affects their bottomline. Although most coverage and research have been done primarily by niche market groups, even McKinsey early in 2015 put out this big report, touting real data: http://www.mckinsey.com/insights/organization/why_diversity_matters. If you'd like to discuss diversity hiring practices through various stages, shoot me a call!
I understand your challenges, clients I speak to especially out in the Midwest are slow to adopt these kinds of policies. I think the better way - and I'd be happy to hop on a call for this - is for you to be a consultant to the minority vendor themselves, and train them in marketing and niche positioning strategies. Let's talk about this!