I once read a great quotation, which unfortunately I can no longer find (so I understand if you vote this comment down for spreading rumours), from a person involved in the anti-fat movement (AHA, USDA, or something like that). The quoted person said that they knew perfectly well that which fats one eats is far more important than how much fat one eats, but that saying ‘Make saturated fat [and trans fats, but this was before people talked about that] a low proportion of your total fat intake.’ was too complicated a message for the public to understand, so it was better to use the less accurate but more easily grasped rule ‘Make fat a low proportion of your total calorie intake.’. (The article did not explain why the second rule would be easier to follow. It is easier using current nutrition labels, at least in the U.S., but that's the anti-fat movement's own fault!)

Also, the anti-fat argument was originally against heart disease, not obesity. Saturated fats (and trans fats) seem to contribute to heart disease, not to obesity. (Of course, obesity also contributes to heart disease.) The main diet-related contribution to obesity is simply total calories, for obvious reasons. Fixing the number of calories, a high-fat diet can actually be helpful (when the issue is obesity), since fats do a better job than carbohydrates of making one feel satiated. The idea that ‘Eating fats makes you fat.’ appeals to people, but it's a fallacy that I've never heard from any authority more sophisticated than a fast-food commercial.

I eat a mostly vegetarian diet, for mostly ethical reasons (which are as much about the environmental impact than animal rights). But I don't try to avoid fats. On the contrary, oils and nuts are a big part of my diet, and I wouldn't have it any other way. Otherwise, I'd be hungry all the time!