I don't see why some consider this unethical and abusive to the CL community. It's just arbitrage; same as in Foreign Exchange markets. It tends to pop up because values are just opinions and to forget that leads to misdirection.
Someone who appears trustworthy + guaranteed quick turnaround would be worth the difference in return for me - I've disposed of old appliances by paying a removal company to take them away on more than one occasion because I didn't want to deal with the hassle of something like CL even if it meant I might make some money back.
I think in the long run there's a lot of opportunity for repeat business there from people who don't need to make the most cash out of the sale as opposed to either make it quickly or just want to get rid of the item without fuss.
Does he actually tell people that he's just going to resell whatever he picks up? I'm sure there might be some people that are uncomfortable with that.
He's providing a service to them. He takes the stuff away, and doesn't charge them to do so. He might even give them some money. (Compare that to hiring a dumpster / skip.)
I don't think he takes landfill material since he is able to sell it on craigslist for money only a day or two later.