This is unfair, and akin to branding anyone who takes medicine as being unhinged.
There is evidence we can extend our health spans. By how much and how are open questions. And if we can actually stop aging, versus slow it down, has not been demonstrated. Some people engage with this unhealthily, just as many terminally-ill cancer patients unhealthily engage with long-shot treatment options. That doesn’t make everyone taking those treatments delusional.
I’d hope we more mature as a society than decrying real medical research that could materially increase our health spans because they’re heretical.
The fact that something happens doesn't mean it's a law of anything. Cars didn't exist before we built them - no law of "no cars". People died of TB before we had a cure - no law of "TB". Same for various types of cancer.
In practice when someone says "live forever", they don't mean to imply they'll live the 10^100 (or whatever the guestimates are) years to the end of the universe. They mean they'll stop aging in the sense that we do now. Maybe we could live to 10,000 or 50,000 or whatever. You can always get hit by a bus, or get some strange disease from a bat, or whatever.