You're right on this one, but you're not the first one to address this problem.
There have been dozens of people who tried to open a dialogue in relation to not just Pr.SE but to SO as well. They were all turned down.
And it's not just about the popular questions being closed. They've also deleted mega-popular and wonderful questions from Stack Overflow with the age of 2-3 years. Magnificent questions with a lot of wisdom and insight. They are all gone now.
I've read all the arguments in favor of deletion and I still find them wrong.
There is a need for a focus in the community. Absolutely. But it must not cross the border to become the dictatorship.
It's true that the site is effectively owned by one individual and it's his call how it should work. However the value of the project like it is with most of the social spaces is exclusively defined by the community which has its habitat here. And it's not quite up to the management to decide what community should look like.
For now it has a huge momentum but you should not deceive yourself. Community places have vaporized in the history of the web. In the beginning you have ridiculed the "experts-exchange" and how they pissed off their users. I say the history is repeating itself. You're going basically the same way. Not to quite that extent - yet - but in the same direction.
Most of the online communities have been destroyed by the management either leaving all of the spammers be or tightening the screw on their members. Recall what happened to Digg when they alienated their users.
I like this place. I really do. It's been a wonderful time first on SO then here on Pr.SE. I would hate to see it go down. And I mean it. But let us be honest to ourselves - it's not that challenging technically to recreate the site functionality, almost anybody can do it. And there have been many similar projects already. For a trigger to fire it only takes to continue acting against the community for somebody to come up at the right moment with the right attitude to take away the angry users. A little advertising in the right places and a new community is born and the old is gone. Recall MySpace. At the time people thought it was going to be eternal - but in a few years Facebook swallowed it by offering a better service. These things happen. Be careful.
And yes, I vote with both hands for the 7th guideline.
P.S. And the very fact that we're even having this sort of a discussion (and not for the first time, but again and again with ever increasing frequency) shows that we have in fact a real problem on our hands. And notice that it is not some disgruntled newbie user going on a rant after his malformed question was closed with the attitude "your site sucks" or something. These are old members, with lots of reputation, who have proven themselves to the community as being skilled both technically and socially and being able to stay focused who keep telling you you're going too far with the closing policy. You may not take me seriously if you want but it's not just me - as I have said there have been other people way smarter than me who keep reacting in the same way. Please listen to them.