This recent TED talk suggests that there is certainly evidence that richer people tend to display meaner behaviours:
Is that because putting other people down is the way to get rich (“greed is good”, etc)? I suspect that it is has more to do with the fact that people tend to want to hang onto what they’ve got; the richer you are, the more you have to hang onto.
Watch to the end though; the presenter does suggest that rich people can be very generous but they do sometimes need a little gentle reminding. It would be interesting to know how charity donations from TED attendees (generally a very comfortably off gr0up), or other measures of generosity, changed among the audience hearing this talk in its aftermath.