I'll take the secret police over secret vigilantes, if for no other reason that the policy of maintaining a secret police force can be debated as a matter of public policy, whereas vigilantes answer to no one.
The thing is though: these guys aren't secret vigilantes. 25 years ago they'd be war-dialing every number in their city prefix ('cause Mom and Dad would get pissed if there were long distance charges on the bill) or moping around 2600 meet-ups trying to show off their homemade redbox.
Now a days they're running LOIC, or WordPress-backdoor-du-jour, or (if they're l33t) `wget --mirror` on some herp derp county website looking for dox. Lists like this are bound to get stumbled upon. When they do, they become currency on irc, redeemable for a modicum of street cred.
Eventually, it falls into the hands of whoever managed to register today's Anonymous twitter account and it gets shoehorned into the political agenda of some teenager who stole "Essential Bakunin" from the library, but hasn't gotten around to reading it.
Secret police are used to stifle dissent; they aren't subject to it. The whole point of a "secret police force" is that they are an incredibly powerful tool not subject to public oversight, public debate, or even public approval.
The "secret" part of "secret police" refers to the hidden identity of the members of the secret police, not that the mere existence of the secret police is a secret.
If the public didn't know it existed at all, it would be both less effective as a means to limit fringe behavior (police states control through fear of not knowing who is working/informing for them), and would endanger the members when they tried to exercise police functions.
Really odd contrast, but even taking it as a given...
Vigilantes answer to the State. Secret police are the State, and the State answers to no one. (Except, maybe, vigilantes, who when successful always seem to become the State.)
Edit: though I'd rather have neither.