That was a pretty cool read.
"I had to keep zig-zagging to avoid pointing the bit which was going to explode at people coming up the street towards me" and "the canal is a crowded place on a Sunday morning"
My god, man :/
Our go-to example in an Economics of Law course was firing a gun while in a crowd. Similarly, attempted murder is a crime even in the case where no harm befalls the victim.[1]
Enforcement should occur up to the point where the marginal cost of extra enforcement is equal to the marginal cost of the activity we are seeking to deter.
I would agree with you that the particular circumstance described in the article does not warrant legal action, but your original post made no allowance for enforcement directed at anything other than purposeful and effective crime.
duty of care?