Because money is the unifying means of exchange, it's the point at which conflicts between different values become apparent. No one actually loves money for its own sake; they love it for the flexibility it gives them to obtain other things. Since people want to obtain different things and all think their own preferences are superior to everyone else's, they tend to see pursuit of money by others as an insult to whatever they consider most valuable. Of course people are much more understanding of their own pursuit of money in order to provide for their families or achieve whatever other goals they may have.