Elmer, it's already been pointed out that sanctions for DUI in the private sector can very well include termination-without the benefit of administrative review boards or union intervention extended to cops. And that the threshhold for 'getting caught' is lower in the private sector than among law enforcement.
Can, but rarely do. Like Elmer, I know many people with jobs like Rock Jock stated that have convictions for DUI or DV, and some have felonies. This is because the decision to fire rests solely with the employer (As well it should), and is thus dependant upon their discretion and vigilance. The vast, overwhelming majority of the time someone can be criminally charged and ajudicated without the employer even knowing, and for your average job they don't have a team of background investigators running updated checks on current employees. Show up for work and no one is the wiser. There are, of course, exceptions to this rule, but they're that- exceptions.
As to the civil service review/appeal process for public sector employees, that is true. However, most unionized jobs have similar processes (though perhaps with less 'teeth'). The point remains, however, and is valid, but is no more valid for cops than for any other civil service employee. In fact, it remains less so, perforce, because of the Lautenburg Amendment. No cop can have a DV conviction on his record, period, because he cannot carry a gun. AFAIK, there is no relief from disability for this. Furthermore, as Guns_and_labs pointed out, there are several other offenses that negate civil service protection.
As to Vernal45's list of cases, note the common thread in all of them: the charges were dismissed. This happens quite a bit in DV cases (for cops and non cops) because it is often a case of "he said, she said" with ambiguous physical evidence, and victims often fail to follow through with the cases in any event. Had those cases resulted in convictions, those officers would have to have been terminated. Now, if there is evidence of prosecutorial wrongdoing in going light on the officers as offenders, there might be a point to be made. Most of the time the opposite is true- the prosecutors go harder because the chief prosecutor likes his cushy job and elections are rarely far off.
Mike