Actually, that answer would very likely be appreciated as long as you phrased it politely. I've very often told people on Stack Overflow that they were asking the wrong question, told them how to start off on the right path, and gotten the checkmark for it.

(I actually will sometimes answer the original question if it's not too involved or impossible, and include a note along the lines of "See this? This is why it sucks for what you want to do.")