Some suggestions for better handling CDN spam:
1. Instead of saying "We're not a CDN", provide a guide where people can copy-paste a CDN link that isn't yours. People don't care that you don't host it, they just want a quick solution, so nudge them.
2. When hosting the minified, etc. files "not for CDN purposes", do so on a changing subdomain so that you can periodically invalidate spam from people who mistook the free download link from the CDN link, simply by removing the DNS record. If you're not opposed to CDNs (I am), just make the download link a CDN link.