Well only in a sense - there are high fibre diets that are also high carb. Carb free tends to be meat based, high protein. At least a diet high in fibre is reasonably good for the gut, providing it is the right kind - soluble rather than insoluble.
But you are completely right that too much of anything - or too little - isn't good for us. Research is actually backing up the basis of Paul Mckenna's 'I Can Make You Thin' program - eat mindfully, eat only when hungry, eat what you want, stop when full. I hate the division of food into 'good' and 'bad' and I could weep whenever a friend says 'I'm being really good at the moment' meaning, I'm calorie counting and eating cardboard.