The seriousness of an idea cannot be perceived solely from its content: seriousness also comes from who expresses the idea and who responds to it.
If the only people who ever discussed gravity were patients in mental hospitals, gravity would not be thought of as a serious idea. Outside of mental hospitals, not only would there be no supporters of the idea of gravity, we wouldn’t even talk about it. This doesn’t mean the sexism of icebergs is a serious idea simply because some tenured professors have published a paper on it, but it does mean the gravity being discussed solely by mental patients will never even have a chance.
Eugenics–meaning, the top-down enforcement of who may reproduce with whom in order to control the health and intelligence of future generations of humans–was once a serious idea, openly supported by intellectuals and included as planks in major political party platforms. The idea’s content has not changed much, but it is no longer considered serious, because now it’s only earnestly talked about by neo-Nazis and (to the extent I’m not being redundant) nihilistic teenagers.
Conversely, many of what we now think of as serious ideas started out as not-serious ones. In each of those cases, the transformation happened because the set of people expressing and responding to the idea changed from “a few crazies” to “many normal people.”
If you have an idea you think ought to be taken seriously, then your job is to dissociate as completely as possible from the crazies who already like your idea (they might even have to be “purged”) and to sell your idea to everyone else, who won’t buy it as long as crazies are still waving its flag.