"Why did you give our enemies the nuclear codes*? Now our country is going up is flames?"
"Well, the truth is that the code is 50285193, and the code destroyed our country, and that which can be destroyed by the truth should be"
*I don't know how nuclear codes actually work. I'm giving a counterargument to "that which can be destroyed by the truth should be"
I still think this should not be assumed to be true and used as an argument. If there is a reason that that which can be destroyed by the truth should be, use the reason as an argument instead.
I agree. Assuming the statement refers to beliefs, and the being hearing the truth doesn't discard them unless they are disproved , it reduces to "false beliefs should be destroyed", which seems obvious in most cases, losing the appearance that it is an actual argument against holding false beliefs.