More Human Bondage for the Public Benefit

— For a sec I though Matt was being facetious, until I got to the middle:
And of course one should be honest. A big part of the notion here is a nefarious leftwing scheme that hopes to use mandatory service as a mechanism for producing social interaction across class, regional, and ethnic lines so as to produce a more solidaristic generation. The thought, both mobility-wise and solidarity-wise, is that the “greatest generation” of conscripts built a nice, relatively egalitarian, middle-class society on the backs of GI Bill benefits and a general sense of social cohension.* Of course, they had an apocalyptic war to create the need for conscription and we do not. Nevertheless, through a sick millenial perversion I (and others like me), believe the positive externalities of conscription justify re-implementing it anyway.
Unfortunately, I guess Matt is being facetious about “sick millenial perversion.” But there is indeed something, um, unwell, about Matt's thought here. I have grave doubts about his empirical claims about the potential net benefits from conscription, but I'll set them aside. What really offends against liberal sensibility is that Matt is clearly unimpressed by the fact that concription systematically denies entire classes of people their liberty and autonomy, and blithely assumes that this sort of mass revocation of fundamental rights may be justified by a balance of positive externalities. To make matters worse, the thing that makes Matt's externalities “positive” do not seem to be neutral to competing conceptions of the political good. No doubt Matt has a special penchant for “solidarity” and “relatively egalitarian” societies, as do “others like him.” But it is distinctly illiberal to use state power with the specific design of inculcating a pet conception of the political good. And it is massively, DIZZYINGLY, illiberal to use state power to systematically strip citizens of their basic liberties in order to promote pet political values.
I can imagine positive externalities that might ensue from a policy of identifying and preemptively imprisoning teenage boys statistically most likely to later commit crimes and disturb the peace. Should we do it? Matt's proposal is morally no better, and probably much worse.