Sorry - Take a look at the world and where the denizens of such schools tend to end up.
As a product of a minor public school myself, I find this obnoxious, Nathaniel. Yes, there are many people in banking, politics, business, etc. who come from this type of school - but then there are also many people in politics and business who don't. I also know of a lot of alumni of such schools who are working abroad for charities - both International and National; as well as in education, health, welfare, prison reform, ... in other words the whole gammut of working experience. As such, the vast majority are no different to the vast majority of state school alumni.
In positions of superiority by right of birth - considered to have been brought up to those positions almost from birth, to have been given high standards of behaviour etc with their mother's milk.
You have clearly had limited experience of such pupils. Yes, there are those who seem to feel that society owes them a living (but the same can be said of a comparable proportion of state schools pupils), but many come from backgrounds whereby parents have chosen to put their children through a good education at the expense of expensive holidays, personal treats, and other home comforts which many people take for granted.
Oh, I expect to find them drunk and pissing on the populace from a high balcony and using the law of the land to thieve from others, not this kind of thievery.
In other words, you expect them to behave like most kids tend to behave at some stage of their lives.
To return to the OP, it's worth pointing out that 'Museum curators say some visitors try to pilfer artefacts as souvenirs.' This nothing new, and suggests that these two were no different from other people, adults included.
