If your Ethereum has stolen, for your Ethereums not to be used by hackers.
A fork coin produced to made for provide security.
I think it's very logical.
As far as I seen till now, all forks no matter which coin, both previous and new coin have value. So your logic may not withstand. Hackers can still sell old coins and make money.
Also is is nearly impossible situation when whole blockchain of coin gets hacked. Generally some users or website get hacked. I don't think non-affected members will support fork to help affected members without any reason.
Now third situation. Suppose a coin get hacked. Now if fork happens afterwards, hacker too have supply of new coins. Hence idea of fork fails.
So I don't think it's logical.