You look down on those who have no understanding of a different opinion, and you are the first to put yourself and your opinion before everyone else. Seems a little hypocritical.

About signature advertising. I remember some earlier days when some (later turned into serious ones) brands started from here, and one of the first steps was to start advertising through a signature campaign. Don't look only from the point of view of those who will spam the forum for a few dollars, try to see the wider picture.

There is no guarantee that the forum would be of better quality without a signature, I'm pretty sure it wouldn't be. Some of the quality posters would reduce their activity or leave the forum because there is no possibility of earning, by reducing the activity, a good part of the quality posters would also go to other places where the discussion is more active, and you can guess where it leads. As for spam, it will not necessarily be significantly less, because spammers will still want to leave referral links or backlinks or whatever to improve SEO for their site.
Quality moderators will leave with a decline in activity, which will enable SEO spam to survive. The most common scenario of many once-large forums that are now on the edge of the margin

Otherwise, you have the option to turn off the visibility of the signature, if it annoys you so much.