I see nothing about your explanation that says we should give the one entity that has the power to take away our liberties with violence more power then necessary.
Again: The state's claim is to legitimacy. A capricious exercise would be an abrogation of legitimacy.
Using force outside prescribed circumstances, beyond necessity, or to serve perverted ends (e.g., benefiting a specific politician, bureaucrat, or political supporter or special interest) would be a capricious use.
Again, read Weber's definition, and I strongly recommend listening to David Runciman's explanation. I came across it long after coming to a similar conclusion myself, he addresses virtually all my own understandings and concerns especially clearly.
