I'm not convinced the onus should be on one side to prove why something isn't an existential risk. We don't start with an assumption that something is world-ending about anything else; we generally need to see a plausibly worked-through example of how the world ends, using technology we can all broadly agree exists/will shortly exist.
If we're talking about nuclear weapons, for example, the tech is clear, the pattern of human behaviour is clear: they could cause immense, species-level damage. There's really little to argue about. With AI, there still seems to be a lot of hand-waving between where we are now and "AGI". What we have now is in many ways impressive, but the onus is still on the claimant to show that it's going to turn into something much more dangerous through some known progression. At the moment there is a very big, underpants gnomes-style "?" gap before we get to AGI/profit, and if people are basing this on currently secret tech, then they're going to have to reveal it if they want people to think they're doing something other than creating a legislative moat.
If we're talking about nuclear weapons, for example, the tech is clear, the pattern of human behaviour is clear: they could cause immense, species-level damage. There's really little to argue about. With AI, there still seems to be a lot of hand-waving between where we are now and "AGI". What we have now is in many ways impressive, but the onus is still on the claimant to show that it's going to turn into something much more dangerous through some known progression. At the moment there is a very big, underpants gnomes-style "?" gap before we get to AGI/profit, and if people are basing this on currently secret tech, then they're going to have to reveal it if they want people to think they're doing something other than creating a legislative moat.