Should dealers be able to......

IMO yes: dealers should be able to email Audiogon members. I receive them regularly & find them to run the full range from very worthwhile to useless. Overall these communications have provided some good information that I'd much rather be with, than without. The mails that I don't find useful - well that's what the delete key is for.
If you find yourself on a monthly newsletter mailing list that you'd rather not receive, simply reply back you want off the list. They are required to delist at your direction.

Tim: rethinking this --- I believe you're referring to the "Tek" situation, which I can certainly understand you not wishing to receive mail from this 'dealer'. Per S7 suggestion above, there may be a way to block reception from specific email addresses although I don't know specifically how this is done? Your application will of course determine the specifics required.