Just go ahead and downvote it instead of whining. Either the link was to something useful and relevant or it wasn't.
The fact that there's an affiliate link has no bearing on that.
If someone's spamming the site with affiliate links, they ought to be banned. If someone posts a link with one from time to time, I see absolutely no harm in it. I think it's pretty clear what's what.
I'm not whining, it's just in bad taste. I actually up voted your post because it was useful, and I DID buy that book this morning (just not through your affiliate link).
This isn't the place to be using undisclosed affiliate links. Had you disclosed it, I would have happily bought it through your link as it would be a legitimate referral.