Seeing as the kingsnakes.com forum site is dedicated to exactly that, there's no deceit there.
Using a generic term does not give other site a monopoly on the name. It's no different than one person choosing monstertruck.com and another choosing monstertrucks.com.
Now if you were the owner of the Bigfoot monster truck, and registered BigfootTruck.com (based on your trademark) and someone registered BigfootTrucks.com in order to ride on your trademark that's an issue.
If adding S is deceitful and ignorant then this site would be in trouble too. People need to get it through their heads that just because you paid 10 dollars for a domain name doesn't mean you own that word.