The Mackinac Center is pro-free markets, not necessarily “pro-business.” The following excerpt from an article by Luigi Zingales does a good job of describing the difference (although the Center is not a lobbyist, either). Zingales is a professor at the University of Chicago Booth School of Business. 

Most lobbying is pro-business, in the sense that it promotes the interests of existing businesses, not pro-market in the sense of fostering truly free and open competition. Open competition forces established firms to prove their competence again and again; strong successful market players therefore often use their muscle to restrict such competition, and to strengthen their positions. As a result, serious tensions emerge between a pro-market agenda and a pro-business one, though American capitalism has always managed this tension far bet­ter than most.
. . . In most of the world, the best way to make money is not to come up with brilliant ideas and work hard at implementing them, but to cultivate a government connection. Such cronyism is bound to shape public attitudes about a country’s economic system. When asked in a recent study to name the most important determinants of financial success, Italian managers put “knowledge of influential people” in first place (80% considered it “important” or “very important”). “Compe­tence and experience” ranked fifth, behind characteristics such as “loy­alty and obedience.”