I don't necessarily disagree with anything he said either, it's the framing and the context of it that I find troubling, and susceptible to co-option.

I agree that men of faith ought to pursue office, but not to propagate that faith--to execute the office faithfully in accordance with righteous laws. Political office, in other words, is not "kingdom work" -- unless one means the common kingdom -- it's not "redemptive kingdom" work. As you said, that's for a different institution, with different means, and different (higher, eternal) ends. Justice, on the other hand, is not a uniquely Christian principle.