By the same measure, much bigger majority of people aren't child abusers as compared to just parents.
Yes...?
Every government, by definition must oppress to some extent.
Indeed. Government is a necessary evil. But that absolutely does not mean we should give them unlimited power. What power we do give them must be necessary and small. We must never let them engage in collective punishment (even if it's "for the children"), and we must never let them infringe upon our rights (again, even if it's "for the children").
Then again, I'm not really sure what your point was. But I've seen people who believe that because the government has the ability to do X, it should also have the ability to do Y (even if X and Y are quite different and one is a more oppressive power than the other), too.
We have a very good example of how that works in Somalia.
The US is not and likely never will be Somalia just from limiting the government's power and not allowing it to violate our rights.
Like communism, it would work very if people were beings naturally inclined to think of greater good over short term personal benefit.
And that's exactly why giving the government too much power is a bad thing (note that I said "too much"). This has more to do with human nature and history. We've all seen just how much damage governments (and a complete lack of government, for that matter) can do.
I think it becomes a problem when the government is harassing entire groups of people (in this hypothetical case, parents) because of what a minority of them do.