The idea is that much harm comes from letting people walk, just because the police did an honest mistake. Or even a willful, outrageous thing.
Punishing the police officer should be enough to deter such behavior.
I think that it's a reasonable stance, but I'm not invested into it much.
I tend to see it as another example where we try to find a reasoned and weighted position, whereas America usually takes a very black and white approach.
I don't mean that disparagingly, it's a valid position. Just an observation.