I agree that it's catty, but it's a way of pointing out that the original comment didn't provide any reason to believe the extremely speculative prediction that it stated as fact. That itself is glib, low quality commenting and it seems fair to point it out. There's no onus on the responder to provide a reason for disagreeing when no reason was given to believe the statement in the first place.

Debate is hard on the internet, but fortunately it's a temporary inconvenience because in future the infrastructure will be replaced with direct neural connections, turning the entire human race into a single giant mind with one coherent worldview.

What is there to agree with? The parent comment is an assertion about the future presented without evidence. ‘Citation needed’ might come across as snarky, but it’s a valid point.

Sorry, it seemed pretty obvious to me. I have now added some examples of present day work - Google might be able to help you find more.

:)

The glib response to that "citation needed" is "Sir, or madam, this is not Slashdot."