Honestly I believe there's a puritan streak in the aspartame controversy; you don't deserve to experience sweet taste if you're trying to avoid sugar, you need to suffer for your diet, and it's unfair to have a zero-calorie soda that tastes good.

I could be convinced otherwise by data, but when I'm seeing decades of attempts to prove it's dangerous and none actually pan out, I'm not going to feel bad about drinking a few diet cokes a day.

Nothing else explains the observed cultural confidence in putative harm than this "puritan streak", combined with sugar industry lobbying. It's gotten other sweeteners like cyclamate and saccharine banned (or voluntarily withdrawn pending a ban) over the years. The same comments are repeated about every new sweetener coming on the market.