someone on my bodybuilding forum (different site) said if you have to do cardio to stay slim, your eating too much? the thing is, i dont eat that much at all...i eat enough. what do you guys think about that statement?

You do cardio to increase your calorie deficit. Cardio isnt required but its much better to eat more and do cardio to create the deficit. It would be "too much" if you werent doing any cardio, but you are so you have nothing to worry about if your progressing. If your not, either eat less or do more cardio / training.

Also, Cardio is just that cardio, it's for cardiovascular health to strengthen the heart. The old school used to say that only aerobics aka cardio burns fat, but now we know differently. Cardio is beneficial in it's own right though for the sake of building and maintaining a healthy strong heart as well as some fat burning, but weight training burns far much more fat and sustains your metabolism for a longer period after your workout.

It was a great moment in marketing when they stopped calling it "aerobics" and started saying "cardio."