They're not suing customers. Flippers are buying them, but they're not customers. They're marking the cars up, and immediately selling them to some sucker for more money. The second owner in this case is the true customer, who probably would have been happier with Tesla if they could have just gone straight to them and paid the actual price.

By that same logic, it's fine to make negative public statements about customers who died using your product, because they're dead and won't buy any more products from you.