Manufacturers pushing their products and agenda in the forums.

I share your view and had suggested a couple alternatives to Admin- if somebody is posting as a dealer to peddle or promote, they should have some badge identifying them and charge them for that privilege (in the same way as "Insider"). For those manufacturers or dealers who are kind enough to offer technical or other advice without the sales job, perhaps they can do so under another user name (though that kind of puts the crush on some long time members here who can wear both hats and provide technical or other advice without an agenda). And having a strict compliance rule that is enforced by user flagging if someone is flogging stuff through the forums without paying for the privilege.
My suspicion is that somehow Audiogon sees value in having dealers and manufacturers and I generally do too-- If Audiogon can monetize it (which is really what this site is about, right?- nobody offers this platform simply for the sake of providing a place for us to ’chat’), perhaps they can figure out a way to separate the two intelligently.
At bottom, how much money does Audiogon make from the forums? Advertising, I suppose. But the original main mission was as a sales exchange for gear, much of it used (I remember when a dealer first said, "I’m getting out of taking trade-ins, just put it up on Audiogon").
As it stands, I just ignore certain threads altogether-- though that may not mean much in the overall scheme of things. I’m sure that Admin is aware of the issue. I think it is a question of how Audiogon can do this sensibly without wholesale disruption.

I don't view it as protection for anyone but myself- to avoid the noise. My alternative has been simply to avoid some threads altogether. I'm not sure it is a question of free speech since that isn't directly applicable (so far) to private internet fora, no matter how "public" (though there are some fascinating legal and policy issues that I will not go into to avoid censure for violating the terms of use here).
I think the issue is whether the forums are an appropriate place to "sell" and in more extreme cases, disparage other brands of equipment when there is an obvious commercial agenda. I had recommended that this be monetized and badged rather than simply censoring manufacturer or dealer postings in wholesale fashion.  
Like @elizabeth said, most of us, I think, can sort the wheat from the chaff. The question (to me) is the tenor or culture of the board. 
As I probably mentioned at some point, I was a sort of consigliere to one exotic car board some years ago and it was a constant headache. There is no easy answer, but part of it, in my estimation, relies on the culture of the board as established by the forum owners, which in turn, results in a form of self-moderation. People who frequent a forum then know what is within bounds and what isn't. Self-moderation, once rules are clearly established and enforced, is in my view a far better alternative for everyone, including those who have the thankless task of moderating, and makes the board a more enjoyable place. 
I'm only one voice and expressed my view, which coincides with the OP. Others may have different views. I think that was the point- and I would hope, as long as we keep this discussion civil, the moderators will not see the need to delete it.

@cleeds - au contraire- I said it should be monetized and badged, rather than wholesale censorship. 

The culture of a chat board is measured by its members, not the moderators. 

I'll tell you a short story about my experience at Audiogon and leave it at that. I lurked here for several years but signed up in around 2005 because I had a question about transitioning from Crosby Quads to horns. Fred Crowder was kind enough to respond- he had made the same transition and I got other helpful responses. Since then, I've learned and also shared knowledge where i can. 
Perhaps it's a change in the tenor of the place or my personal take on the threads, but there seems to be a signal/noise problem. I can ignore threads of no interest and disregard posts that don't add to my knowledge. 
But, to me, the value of the forum is sharing knowledge and experience in a constructive way. That doesn't mean no criticism or disagreement- to the contrary, that's where learning happens. But having lived through the early Internet wars over content removal, ISP responsibility and Net behavior, perhaps I'm just played out on the site.  
my regards,
Bill Hart