> aspartame has basically zero negative effects ...diet cola is much safer than real cola.
I won't argue that sugar isn't bad for you, but I don't think the science (and my own observation) agrees that diet cola - specifically aspartame - is "much safer" or somehow healthier. The linked WebMD page mentions this:
> The study found that consuming a low-calorie sweetener was not, by itself responsible for slowing metabolism. However, when combined with other carbohydrates, or fats, the consumption of the non-sucrose sweetener did lead to a significant drop in metabolic rate.
We don't generally ingest things in isolation, so you have to account for what an ingredient does in the context of an average diet accompanying the ingredient, and in that sense, aspartame absolutely does have significant negative effects. Those effects may or may not be worse than real sugar, but after the whole switch from "margarine is a healthier butter substitute" to "turns out margarine might be worse for you than butter" (and other similar upended dietary advice), I'm personally included to prefer sugar - in moderation - over sugar substitutes.
And that's another problem with sugar substitutes: claims that they have no negative effects encourage people to consume "diet" products in very high amounts - often more than the products they replace, so you're no longer comparing equal amounts of the substances. For me, drinking a sugary soda is an infrequent, deliberate decision - one I don't take lightly. There's a guilt that comes with it, but I think that's a good thing to make me think twice. But I also see people drinking diet soda all day, every day, thinking there are essentially no negative consequences (when there obviously are).