JO doesn't want to drive these guys out of business. He just wants to trash their stock so he can buy it.
RJ's are cheap right now, why not fly below cost, weaken an airline, and then buy. Heck he won't even have to worry about scope with UAL/Delta/USAir.
He's not alone. Watch Republic and Skywest. They all want to grow beyond "regional service". The funny part about all of this, is that UAL/Delta/USAir are financing their future competition. ACA was the first but certainly not the last. ACA picked the wrong time and only used one certificate.
Many people feel that ALPA giving up scope on the RJ's was where it all started. I think the down fall of the majors (outside of deregulation) started when they started farming out flying to other airlines.