Bad behaviour expands to fill the space that is available to it.

Bad behaviour is constrained by laws and policing, but the most pervasive, important constraint is societal pressure: what most people expect and accept as proper behaviour.

When bad behaviour is not resisted, it expands until it meets resistance. This is the same law of human behaviour as bullying.

The weakness that allows bad behaviour can be situation specific, so a once-off failure that permits an event or allows a chain of events to begin.

Or it can be long-term, like allowing a child who is inconsiderate and bullying to get away with it, leading to persistent patterns of adult behaviour, especially abuse.

So it is the responsibility of society – meaning individuals – to set acceptable parameters of behaviour and to intervene – to apply social pressure – when they are crossed.

The majority of people respond to social pressure and remain within the boundaries of its resistance: see “The 10-80-10 rule of good behaviour“.