Generally, it's not. However, our company's owner is a gun nut, too, and doesn't mind in the least. When our IT guy put a lock down on websites categorized as "weapons," the owner called him into his office to show him how frustrated he was at trying to find a gun part with everything blocked, and instructed him to immediately remove that category from our firewall system. About half of our company is indulging in some manner of gun porn on any given day. My computer monitors are facing a wall so only I can see them anyway, unless someone walks around behind my desk. It's probably a moot point, though, as all the computers in our Quality department have various gun pics (porn) scrolling through as screen savers.
... and yes, "porn" is simply gun pictures I enjoy viewing.
Maybe we should change the titles on the picture threads to things like "Revolver Porn Thread," etc.