Attitudes like these greatly inflate the actual incidence rate of outright illegal abuse of internet services, most notably child porn. There is not a pedophile lurking for open wifi on every block, as popular hype would have you believe. (By contrast, there often IS a violent domestic abuser lurking on every block in US cities, yet nowhere the same magnitude of public shame campaign directed against them, despite the magnitude of their damage to society.)

Also, downloading copyrighted material generally amounts to a civil offense in the US, even though it is often conflated with more serious criminal behavior (aka child porn) by the MAFIAA.

The risks of running unsecured wifi can be easily communicated to its users, and likewise contained by promoting use of secondary encryption such as SSL.

To claim these risks are so grave that people running unsecured wifi must be idiots is comparable to saying that people who leave their personal cars parked on city streets are also idiots, since those cars be stolen and used in violent crimes.