Manufacturers pushing their products and agenda in the forums.

I don't care for the vendors that do the things you mentioned, but I'm sure there are some that appreciate their posts. 

Some people know how to use social media to build their reputation as experts or thought leaders, and some manage to tear down their reputation by misusing social media.  IMHO the posters you described are doing themselves more harm than good and aren't savvy enough to see that.

As long as this place doesn't become a complete spamfest, I don't think they should be banned or restricted as long as they're offering some educational content that may be of value to some members.  

I find the tactics you mentioned offensive and would not do business with anyone that conducts themselves in that way.  Others may see it differently.  

elizabeth

I am of the opinion that no one needs to be 'saved' from whatever.

I agree, but this is a common problem. Someone identifies a group that they decide needs "protection," and they then appoint themselves as the "protector" of the group that doesn't recognize or even necessarily want the "protection." Meanwhile, the self-proclaimed "protector" claims the moral high ground.

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.