Is Constantinianism all bad?

"Constantinian" has lately been a favored pejorative in
theological circles. The term--an allusion to the fourth-century Roman emperor
whose conversion to Christianity turned a marginal sect into a state religion--has
been used to deplore any alliance between the church and the state or, more
broadly, between the church and the dominant political culture.

Thanks to the influence of John Howard Yoder and
Stanley Hauerwas, among others, anti-Constantinianism has provided an edge of
energy to much mainline preaching and theology and has fueled a healthy
suspicion about ways that churches can lose their identity by aligning
themselves with power or the mindset of modernity.

But is Constantinianism entirely wrongheaded? Don't
Christians want people in power to embrace Christianity and Christian values?
Is it a bad thing if they do? Is it impossible or meaningless for them to try?