I think it's too early to speculate but a lot more was at stake. If the blackmailer had released compromising information about SR users this could result
in a lot more broken families.
It seems to me that as a libertarian, DPR was acting within the
non-agression principle.
No way. Seriously, that should be a no brainer. Blackmailing isn't an aggression, so no use of force against a blackmailer is acceptable. Just study ethics before saying such things. Here, start with Walter Block:
https://mises.org/daily/4576If after the revelation of such secrets, bad things happen, that's not the direct action of the blackmailer, but of those who took the bad actions (the government, in this case). The blackmailer isn't violating anybody's rights. You have no "right to keep secrets". Having a "right to keep secrets" implies in having the "right to censor", by the way.
Thanks, you may have a point, I'll have a read of that link.