I think part of the problem today is the ubiquity of twitter. I suspect some of the more naive fans feel that getting constant twitters ("I'm getting into a taxi!" "I'm having lunch at El Trendy!" "I just bought the cutest shoes!") from celebrities means that they actually have a relationship, or at least a vested interest, in their celebrity of choice. So, when their "BFF" lets them down in behaviour, they react in a very personally-insulted way.
A married man and a young woman did some "canoodling". This, by itself, may be considered reprehensible by many, but not uncommon enough to fuss about. However, when someone gets on the Fame Train, their publicity machine has a goal - make the public consider their every action significant in some way. If they behave badly, the public will respond negatively; this is the price of living one's life demanding the public eye be upon one.