Well no, he's not asking Alienware to fix anything for him (under warranty or paying directly), he's just simply asking to buy a spare part from them so he can fix it himself.
It's more like buying a used car from someone, trying to buy an oil filter directly from the dealership, and being refused because you're not the original (authorized) owner of the car. You're not asking them to change your oil, which would give them a reason to check your warranty information to make sure everything's in line, or recording your VIN number in their system so they can keep track of what car's they've worked on for the day, he's just someone who wants to buy a part from them. They're just telling you they can't sell you an oil filter because they don't have a record of you buying the car from them.
Really, why should he even be required to be the owner of any Alienware merchandise to buy a replacement part for the laptop? I'm not entirely sure of what he told the CSR's on the phone, but I wonder what they'd say if I called up and wanted to buy a replacement glowing alien head (from their laptops) to decorate something in my house with. Will they deny me because I'm not an authorized owner of the laptop that the glowing alien head fits on, or will they gladly sell me the part regardless of whether I own one of their laptops or not?
If they're denying him the part because he wants it replaced free under the original owner's warranty, that's one thing. Refusing to sell him the part because they have no record of him buying anything directly from them is different.