We do not have any data that proves your theory. We have data that shows many cases of hacking, and we can summarize these amounts to arrive at a quite big number. But when it comes to human errors most cases are small anecdotes, reported in different parts of the internet. They are mostly stories, we can't even confirm most of them so that data is very weak and unreliable. So we have both things, the amount that was stolen by hackers is much bigger than the self-reported human errors and these amounts are much more reliable than those reported by humans. Someone could tell a story how they made a mistake and lost 500 BTC, but why would we believe that without any proof? People make up things all the time.
Still, I think that in the long term it is possible that the human error outweighs the technical hacking. It does not have to be, we will see what happens. We could make some model projections to get better speculations about this, but it would still be speculation.
Human error is not really a threat to Bitcoin, unless that human error comes in the form of a really bad development mistake that sneaks through all eyes and ends up in a new release.
He is more focused only on this question, and not like a threat to the whole of Bitcoin even if you are right about what you have written there.
For me, human mistakes cause more Bitcoin losses than technical attacks.
What do you guys think?
And he is incorrect about this, there is no place for subjective opinions on this. Data proves or disproves such a claim. We can make subjective statements or have opinions on what the data means or what the future will have, but for the current situation the answer to this question is quite clear.