Okay, I got that. However, calling it a problem is a rather bold claim. I would call it a property of PoS.
It is more than a "property" it is an as of yet unresolved problem. There is no security in PoS unless it is resolved.
Let me restate my question. Why should a node 100000 blocks ahead accept a blockchain re-organisation?
(No matter if PoS or PoW)
Um, well no. I can't mine using computing power I no longer have (but did have at one point in the past).
Our mining rigs destroy themselves? I doubt it.
How would want to be on that fork anyway? In doing so, they would destroy every single bit of confidence in that very cryptocurrency.
The cost to the attacker is absolutely zero. If he can gain anything more than zero he has everything to gain and nothing to lose. It would destroy confidence in the PoS currency you are correct especially when it happens over and over and over without end. That is why it is the Pos problem.
Well, as I said this is true for PoS and PoW. Trying to destroy would definitely diminish confidence in the cryptocurrency as such no matter if PoS or PoW.
Your statement about 'no cost' is true as well.
However, the huge advantage of PoS is: the network controls the consensus power and the network can punish the bad guys. I would call this the
PoW problem as the consensus power can easily be introduced from outside without any control whatsoever.