The buyer is not driving them out of business, Ebay is. Why does Ebay need to react so harshly? They should care more about the hardship they inflict on their sellers, and not blindly measure each piece of negative feedback equally.
Blaming the seller is a bit like blaming someone who calls the cops on a loud party, for bad behavior by the cops.
If the cops are known for breaking up parties by beating people to death (and you know of this), don't you hold some responsibility if you call the cops to break up the party? You're not 'solely responsible' for whatever happens, but you have some amount of responsibility.
Blaming the seller is a bit like blaming someone who calls the cops on a loud party, for bad behavior by the cops.