A currently existing social norm basically says that everyone has the right to an opinion on anything, no matter how little they happen to know about the subject.
But what if we had a social norm saying that by default, people do not have the right to an opinion on anything? To earn such a right, they ought to have familiarized themselves on the topic. The familiarization wouldn't necessarily have to be anything very deep, but on the topic of e.g. controversial political issues, they'd have to have read at least a few books' worth of material discussing the question (preferrably material from both sides of the political fence). In scientific questions where one needed more advanced knowledge, you ought to at least have studied the field somewhat. Extensive personal experience on a subject would also be a way to become qualified, even if you hadn't studied the issue academically.
The purpose of this would be to enforce epistemic hygiene. Conversations on things such as public policy are frequently overwhelmed by loud declarations of opinion from people who, quite honestly, don't know anything on the subject they have a strong opinion on. If we had in place a social norm demanding an adequate amount of background knowledge on the topic before anyone voiced an opinion they expected to be taken seriously, the signal/noise ratio might be somewhat improved. This kind of a social norm does seem to already be somewhat in place in many scientific communities, but it'd do good to spread it to the general public.
At the same time, there are several caveats. As I am myself a strong advocate on freedom of speech, I find it important to note that this must remain a *social* norm, not a government-advocated one or anything that is in any way codified into law. Also, the standards must not be set *too* high - even amateurs should be able to engage in the conversation, provided that they know at least the basics. Likewise, one must be careful that the principle isn't abused, with "you don't have a right to have an opinion on this" being a generic argument used to dismiss any opposing claims.
You appear to be putting words into my mouth, but I'm currently too irritated to detangle this much beyond that point.
"Giving people too much credit" was a reference to peoples' desire to be rational. I tend to assume that that's significantly above zero in every case, even though the evidence does not seem to support that assumption. This is a failure to be rational on my part. (I doubt I'll fix that; it's the basis for most of my faith in humanity.)
I make no such assumption about intelligence (I do not assume that people want to be more intelligent than they are), and make a conscious effort to remove irrational biases toward intelligent people from my thought process when I encounter them. I have been doing so for years, with a significant degree of success, especially considering that I was significantly prejudiced against less intelligent people, before I realized that it was wrong to hold that view.
I have also put significant effort into learning how to bridge both of those communication gaps, and the skills required in each case are different. When I'm simply dealing with someone who's less intelligent, I moderate my vocabulary, use lots of supporting social signaling, make smaller leaps of logic, and request feedback frequently to make sure I haven't lost them. (Those skills are just as useful in regular conversation as they are in explaining things.) When I'm dealing with someone who's not practicing rationality, I have to be very aware of their particular worldview, and only thoughtfully challenge it - which requires lots of complicated forethought, and can require outright lies.
The lack of either of those sets of communication skills will make dealing with the relevant people difficult, and can lead to them thinking poorly of you, whether you actually are prejudiced against them or not. Assuming that someone who does not have one of those sets of skills is prejudiced does not, in practice, work - there's a very high risk of getting a false-positive.
A person who is 'thinking' irrationally can only be challeneged to the degree that they're being rational. If they eschew rationality completely, there isn't any way to communicate with them.
What have you actually accomplished, if you use social signals to get someone to switch their concept-allegiances?