There was huge controversy over aspertame (discovered 1965, limited approval in 1983) in the first decade even though the only solid case against it was that it is bad for a handful of people who have the genetic defect PKU.
Sucralose was discovered in 1976 and wasn't approved in the US until 1998.
The strangest case is Stevia which, since it is a natural product, has gotten into heavy use without really being approved as a food additive. (Loose Stevia rebaudiana leaves make a nice sweet tea combined with Camellia sinensis I'll grant that.)
(2) If you were trying to psychologically manipulate people, "autism" is the threat you would use.
That doesn't make it safe, but it's standard that traditional foods are regarded as safe to eat unless evidence emerges that they aren't.