Notes on Specific Laws - the second Law Answered
An unsuitable thread isolated from replies will descend the list into obscurity.
This is an "anti-spam" law. We have all seen threads appear that advertise odd things - trainers, dating sites, Chinese plastic-moulding factories - and we all agree they should no be here. It is tempting to reply to the threads to express our chagrin, but that makes the thread bob to the surface again, pushing more useful threads down.
Far better to flag the thread and let it slide down the list until it disappears.
In addition, this law can also be applied to trolls - if somebody starts a thread specifically to start an argument (as opposed to a discussion), or just to put another user or group of users down, then they are trolling. Those threads should also be allowed to slide.
Addendum to the second law
Spam advertisers may be chastised through the Private Message system to prevent their thread's longevity.
If you cannot resist giving a spammer a piece of your mind, the PM system is very useful - the spammer gets an email alert to your comment, they are aware of your feelings, but the thread is undisturbed.
Similarly a troll may be gently reminded of the site's Be Nice policy via a PM. Should the troll decide to respond with vitriol, they are deprived of the audience they crave.
Finally, you can help the site financially - using a PM to casually point out the correct route for advertising could, perhaps, result in a new fee-paying advertiser for the site.