I don't think that philosophical zombies are a nonsensical line of thought at all. As Ray Kurzweil states in one of his books (paraphrasing), "I take it on faith that the universe exists". Accepting the inability to receive proof of others' consciousness is a major battle in the quest for developing a rational view of the subject.
The pzombie line is "posit the same world as ours, but no one's conscious". At best, it's useless because we don't know what consciousness is. At most likely, it's just dumb and non-sequitur. Like saying "OK imagine this glass of water. It's identical to water in every way. But it's fire. Ah-ha! What does that mean? <spooky voice>".
So either consciousness is based in physics, in which case pzombies are non-starter, or we don't know what consciousness is and it's a pointless conversation.
