It becomes clear because of them. Whether suddenly or gradually, society—through its members' opinions—determines the value of people's ideas based mostly on time and, sometimes, on congruence.
So if, for instance, a never before seen painter is willing to blow the world with his art, he will have a hard time for his art to be seen or respected, assuming that he doesn't give up before this even happens. Respect is mainly about knowledge, consideration, and, perhaps, admiration; disrespect, most of the time, is only about ignorance.
Respect has its logical and illogical components. Based solely upon authority, respect is chiefly illogical, as authority usually erases reasoning and promotes blind following. Based entirely upon reason, respect is completely logical, as the use of reason permits an informed and thoughtful interpretation about reality. Do we ever challenge logic itself? We don't, it would disrespect reason. Even the most dynamic processes have solid, static bases.
Once finished, human products don't change; interpretations do, all the time. Interpretations are not products, they are dynamic processes. When an interpretation about someone else's product (or about someone else itself) becomes fixed, it turns into a judgment. To judge is to label things as "good" or as "bad," according to individual (and usually fixed) principles and values.
Logical reasoning is hard and resource consuming, while following an authority is easy and economic. Respecting someone's products in any field usually starts off with a social and logical consensus about the value of such products; until the time comes, after a successful consensus, for that someone to be considered an authority in that field, and his/her ideas no longer need to be reasoned by most of the people. Some very few, though, continue with logical respect; if some product of that authority is proven to be wrong, to be incongruous with the authority itself, authority is then judged. Sometimes authority falls and gets disrespected by most.
I will keep working on my ideas, hoping to become, at least for some, a reasonable authority one day; never for you, thoughtful reader: it is to the authority of your reason to which I address this message.