I don't buy it.
People refer to them as "macbook" because thats what they are - a mac. Theres nothing else you can call them. Its not a PC, its a mac.
The biggest problem, and the one that has reared its head several times in this thread is that they are seen as fashionable. And thus it attracts exactly the same bile and hate, as those who spend £300 on a tshift because its got a certain designer on it.
Yes it is a PC.
Why is a mac not a PC? What does "Window" have to do with something being a PC? It just means personal compauter, that's exactly what any macs are. Is an Apple "Cinema Display" not a monitor?
It's all about differentiating between "normal" computers and "special" Apple computers. Macs use all the same hardware as any other computer, there is no reason it's not a PC.