Sugar is sugar, really: excess energy that gets converted to fat if your body doesn't need it.
edit: Besides, the sugar in fruit is fructose (which is the "bad" sugar) as opposed to glucose (the "good" sugar). So why do people recommend including fruit in your diet if it contains "bad" sugar? Because they also contain fibre (which sates your hunger) and, obviously, vitamins and minerals.
The trend towards labelling everything fat-free or low fat is completely missing the point (and misleading to boot). Given the choice between a product low in sugar and a product low in fat, you're better off taking the fat hit and missing out on the sugar. Clearly, avoiding too much of either is probably wise - pay attention to the nutritional boxes on things and try to follow the RDI values (keeping in mind that particularly active individuals may need more of key nutritional types).