Nom, i think moshiach must be coming soon, because you wrote something that i actually agree with!
I don’t think it depends on yichus though; i think people who look down on others would do so in a different context, i.e. if they were rich, they’d look down on the poor, etc… it’s a bad middah, like any other. Truly frum people who have worked on their middos don’t look down on other jews.
Actually, among the people I’ve seen who actually look down on others, I’ve only seen it by heimishe people who aren’t particularly knowledgeable who feel like they have to grab on to their yiddish or minhagim that they have, and look askance at someone solely because they’re sefardi or a BT; I’m talking about sefardim and BTs who are just as frum, if not moreso, talk with yeshivish language, dress like everyone else, etc…
An example of this is the fact that roshei yeshiva of chaim berlin and torah vodaas had no issue taking sons in law who were sefardi, and those are just the ones i can think of off the top of my head.
I do agree that newcomers can be more insecure and will lash out more because they feel threatened, and aren’t sure that they are in the right, because if you can’t learn shulchan aruch yourself, and you’re just going by what your rebbe told you, maybe there really isn’t a halacha against the things less frum people do?
For all my online rhetoric, many here would be surprised at how i interact with other jews who aren’t frum or less frum. The same way, and I’m in no way comparing myself, people are surprised to know of a certain rosh yeshiva who was among the most anti-chabad voices in the world, who housed a yechi-nik and his family, some of whom were disabled and had a very difficult life.