Think the fact is they are committing a crime, abstraction of electricity, using a site which they are not entitled to and taking something of value which they should not have. Certainly for the UK.
Ref:
The sites are clearly labelled Tesla only and the principle if you have either paid for it in you car purchase, you have an allowance from Tesla you are using or indeed you are on pay per use. If you are not in a Tesla and in one of the groups then it is theft.
Admittedly somewhat amusing in some sense but lets call it what it is, it isnt a system which is designed for free vend and no one expects it, so when it appears it is clearly a fault. Would be mightily pissed off if I turned up at Superchargers to find a pile of freeloaders blocking the stalls.
Tesla can choose to open the network yes, but until then these people are simply blocking access.