I just don't know what on earth the general public could see as coming true, since the events people saw are all 6 months in the future. Yes, one particular team of FBI who are investigating the blackouts has seen a few things that seem to indicate the visions are true, mainly because of Mark's very specific vision about investigating!--but it's not like that's widely shared public knowledge. Demetri is in a different boat than most of the blue hand people because he's on the investigative team, so he keeps getting confirmation that the flash forwards are true. I'd have to see something like that to buy that the general public is all so convinced that they're forming suicide clubs!