I think you make a couple important points... It is how I feel about spammy posts also. New Users come online and decide how to use the site based on what they see. Then many of them emulate that.
This is why I also flag fairly often now. We have the tools to reward good behavior and to discourage bad behavior. We must start using the tools.
I'd add: if you are going to flag, it may be best to leave a comment as well explaining why.
If not, the flag will probably go unnoticed and they won't realize what they've done wrong. Having the lesson spelled out along with the penalty, behaviour is likely to change a lot faster as they realize the consequences of what inappropriate actions they've been unconsciously taking. ;-)