> From 1970 to now there have been what...4 generations of aspartame consumers?
The few people who started drinking it as teens and adults in the 1970s are now only in their 50s and 60s, and the generations after that have only been drinking it for a few decades. That isn't much data at all to judge long term impacts. 50 years is nothing, and a lot about our consumption of aspartame has changed drastically over that time. In the 1970s people weren't drinking 3-6 cans of diet soda a day. The average American today is drinking a bit less than the 58 gallons of soda a year that we drank in the 90s, but it's still a lot more than was being consumed for the first decade or two since aspartame was added.
Personally, I don't even drink soda and so I have no skin in this game whatsoever. I honestly have no idea what the long term risks of Aspartame are, I just doubt anyone could have much confidence with less than 50 years of research. I can say that it seems highly unlikely that there are dire short term effects at least, but I have nothing but sympathy for those who are skeptical considering that companies routinely buy research to show whatever conclusions they want to see while burying any results that are unfavorable and the FDA often seems to care more about protecting profits than human lives. We've seen again and again that companies are willing to knowingly poison people and that regulatory agencies are ineffective at protecting us from it, so I can't blame anyone for being cautious.
Considering that the WHO's stance of "possible carcinogen" isn't a strong claim in the first place and the recommendation for additional research can't hurt anyway it doesn't seem unreasonable to me.