The onus is on people who claim Gehenna was a dump to prove it, not on others to disprove it.
Normally, yes. But not when a claim was made ages ago and has gone uncontested (perpetuated even) for so long, only to be declared a myth later…
What if my great, great, great grandfather said his dad was named Gabe. But I check the records today and don’t see any evidence for an ancestor named Gabe. Was it a myth?
This is the thinking that perpetuates the Christ myth theory. In other words, I’d expect you to prove Christ existed as the default would be that he did not. You can’t even source Josephus any longer as current scholarship considers those references were inserted by someone else. That is textual criticism for you.
So is an argument of silence always indicative of a myth, or does the timeline not mean anything?
…and like anything a little selective, i.e., Origen’s quotes above, when you read the fuller context all is not as is made to appear by said partial quotes etc. IOW, there is more to the scenario than the “dump” association alone… which I might addt is covered in the full article I linked to up the page.