Generalisations _can_ be used to push "social dogma", but it doesn't have to be, and it doesn't mean generalisations are automatically a bad thing. They are a useful evolutionary shortcut our brains invented.
If I see 100 people with easily identifiable attribute X, and 90 of them are mean to me, my brain makes a useful shortcut in the form of a label and says "attribute X" is connected to being treated meanly, avoid those guys. It's not that I don't know 10 of them treat me fine, it's just that it's less of a problem to miss out on 10 potential friends to avoid having to deal with 90 meanies.
It's probably important to say that I'm speaking as a "brown person", who has been "discriminated" against plenty in my life. I don't make a fuss when I get "randomly selected" every single time at the airport, because they're working with statistics.
• dislike, hostility, or unjust behaviour deriving from preconceived and unfounded opinions
Let me tell you that my opinions on people under 30 are 100% based on reason and actual experience. Some of it is even judgement on _me_ when I was under 30.
Don't take it personally, people just haven't gone through a certain amount of life before 30. It doesn't make them bad, or less deserving of respect. But let's be real, giving someone respect as a human being isn't the same thing as taking their opinions on say, how society should be run, as seriously as someone who's older.
This is of course generalising, as you're going to get a few 21 yearolds wiser than a few 51 yearolds, but that's how generalisations work; they're true in _general_. It's become common-place to see generalisations as an automatic bad thing, but bear in mind they serve a function, and are even how brains work.