Metaphorically, "dry wit" is a form of sarcasm. Being "salty" is also accepted to mean "being bitter" or "full of attitude." I believe that sarcasm can be taken as an example of either trait.
When you have attitude, metaphorically it could be "drying" to ignorance-aka-mold because when poor or invalid arguments are offered forth in comment threads, but then countered by educated, vehement, I-am-not-going-to-take-your-shit-because-no-you-don't-deserve-the-benefit-of-the-doubt responses, I think those responses will often be recognized by the community as apt, just, and even deserved. As a result they will be somehow illustrated as superior to the moldy comment, whether in upspokes, gold/gilding/whatever, upvotes, etc. And when it becomes clear to a user that the community is overwhelmingly against him, which is usually best shown by solidarity for the other option/viewpoint, he suddenly tends to shut up. And even if he doesn't, the demonstration of where the general community's opinion lies allows other, future readers to realize that just because the comment's there doesn't mean anyone agrees with it. in that way, I would say that salt/attitude prevent the growth of mold/ignorance.
Someone who I respect once told me that I "had never been too nice." I guess I have an acerbic reputation. But the truth is that this is not true. The truth is that in the past, I have been far too nice to people and given them far too many chances, far too much benefit of the doubt, and doing so - repeatedly, because I am an optimist - over time has caused me harm.
These, as well as the word "nice" and the heavy pressure society exerts on people to be "nice," are ways that people manipulate others, making people feel bad because they are not going along with the other person.
I think some people bank on the "well you should have been nice nyah nyah" argument to derail from the actual argument.
It does not behoove me to be nice when someone is, in my opinion, blatantly wrong. When someone in your proximity, someone you allow around you, expresses something that opposes your own beliefs, if you do not speak up, that person will think not only that it's okay to say those things but that you either don't mind or tacitly agree with them. The people around you who associate you two will believe this too if you do not speak up. If I have a friend who is a terrible sexist but we don't talk about it because "it's an emotional topic" and we'd rather not, well, guess what? Any time anyone sees me out with my friend and hears him say disgusting things is going to think the same. That is why I do not advocate for staying friends with someone if I disagree with them on social issues that I feel are a matter of basic human rights. It's okay if we disagree about vidjagames or some shit but not essential aspects of how people should be treated.
Attitude, confidence, the willingness and self-righteousness that it takes to speak up when you think you see something truly wrong being said - no they are not always flattering traits. Yeah you can look like an ass. You can be wrong sometimes or misconstrue. I don't care about that. I stand up in conversations like the one earlier because it is important to me to do so. It is important to me to say, "I disagree with this" because if I do not, or if someone does not, it's easy for the whole website to look racist. Or whatever. C'mon guys like this literal thing happened in practice: people kept complaining about racist users and how the site seemed racist. I mean I'm not falling for bait and once a user's shown his true colors I filter him and move on, but I will stand up in fresh conversations with fresh users at least once before I tune them out.
It is important to me to speak up over/in lieu of having happy happy peaceful interactions all the time. I stand up because it's not 8bit's job to deal with all of this shit, either. I stand up because I am trying to put my money where my mouth is and defend what I believe and support people like 8bit who have to deal with assholes constantly forcing him to have the same conversation about racism over and over and over again.
Sure i'm probably idealist and a white knight or some shit. I stand up because I won't shut up and put up.
But I am not tired enough that I will not stand up and say something.
I will never choose being polite over making my point when I am passionately convinced that I am right and the opinion being expressed against me is not only wrong but reprehensible. I don't know what the value is in being polite if it dilutes the point or allows others to avoid it.
Silence is so easy to mistake for agreement, or at least tolerance.