Yeah, you'll have to excuse me if I don't take advice from a site called "rantfood".
Diet Soda isn't bad in itself. The reason that studies show that diet soda makes you gain weight is that if you've gotten used to drinking normal sodas on a regular basis, and suddenly switch to diet, it throws your body a little out of whack and you usually start trying t make up for the sugar cravings in other places, thinking it's okay since you're not drinking sodas anymore, and you overcompensate with the alternative sugar sources.
Me, I quit Mountain Dew a number of months ago, switching to Sprite Zero, and still don't crave sweets because I supplemented my diet with fruit, which has more natural sugars in healthier quantities. Usually grapes and strawberries from the local grocery, but sometimes oranges and apples, too, if I'm in the mood. The strawberries I loved until recently, they've started selling under-ripe ones that are bland as shit and god damned adamantine.