You're not doing anything with the KOOKS.COM domain -- it was just pointed to a parking page, so why not just give it to them?
Over the years, we have developed many of our registered/purchased domains into real businesses. Some of these domains we had for over 10 years before landing on a plan for how to best utilize its name and traffic. We have had plans for Kooks.com from day one, and will eventually develop a website around the domain in the future. The domain is obviously valuable enough for Kooks Custom Headers to attempt to Hijack, but we're not the sort to just give away our valuable property willy-nilly.

Kooks Custom Headers has a Trademark for KOOKS. Doesn't that entitle them to your domain?
No, it doesn't. Yes, they have a US Trademark for KOOKS, but only in regards to automotive and motorcycle parts -- namely, exhaust headers and mufflers. Their trademark provides them certain protection in those areas only, much as Hormel's trademark provided them with protection when it came to canned or potted meat, but not an email spam blocking company.