You are right in thinking that "shoot down" is most often used to describe the action of rejecting, spurning, or defeating something or someone.
However, if I assume that this sentence was written with great care and some significant degree of knowledge of the language, I would interpret "shoot down" as "criticize" or "demean," a less common definition.
Normally, "shoot down" means to refuse or reject but it doesn't really make sense that you could refuse an intention. I think it makes more sense here as "belittle", "criticize" or "mock", which is another meaning of "shoot down."
 I see bibliolept and I came to the same conclusion. (Sometimes I sit on a post for awhile, pondering my answer. I'm not the quickest of minds around here. )