I believe very strongly that if you want to be an ally to marginalized groups, you should absolutely read and watch material bigoted against them.
This is because one of the big things that radicalization pipelines benefit from is the principle I've seen framed as "milk before meat", where they feed you palatable, easily digestible ideas, often with a kernel of truth, in order to work you up to the core of the bigoted ideology. If you go to the meat first, you will choke on it. This will make you more easily able to spot it when they try to feed you the milk, and more resistant because you know the meat it's building up to.
There are two keys. First, you need to start with the meat, and second, you need to read it with a sharply critical eye.
If you're looking to read something fatphobic, for example, Harry Potter may be a great mainstream example, but it's in a way that is so culturally acceptable that it can slip by if you aren't looking for it. "None For You: How Fat People Are Ruining America and the Planet and What You Can Do About It", on the other hand, is rather obvious in its biases, allowing an amateur to see them clearly for easier interrogation of the premise. Most bigoted material can be acquired by piracy or through your local library. This is one of the big reasons that libraries stock bigoted material.
Then, start noting down all of the things that the material says that seem to make sense, or that you are sure are true. There's no shame in this. Bigoted ideas are ingrained in your upbringing, and on top of this, a lot of bigots will take real problems and build on them in ways that are bigoted.
For instance, anti-immigrant sentiment in the USA is often bolstered by the fact that wages in the USA are effectively decreasing, along with job security. They say that this is because immigrants are taking the jobs, decreasing the amount of value that is available to USAmericans. To a USAmerican who does not know much about immigrants, but does know that their paycheck buys less and less, this sounds like a plausible explanation.
Then, later, look up exactly what they are saying. What are the real issues? (Racism and unchecked capitalism.) Why are they being used to bolster this argument? (Because it takes the heat off of powerful people and puts it on powerless ones, redirecting the hate to people it can more easily hurt, which satisfies the rage of the USAmerican, drives a wedge between them and immigrants, and takes heat off of the powerful.) What are real ways to tackle the real issue? (Solidarity with immigrant workers, especially undocumented ones, unions, and working for better social safety nets.) Why did I fall for that? (You did not have enough information.) Can I notice this rhetoric in the future and avoid falling for it? (Yes.)
Know that many of the ideas you encounter will be normal. Much bigotry is normal. Normal is not automatically good or right.
Know that there will be useful ideas interspersed with some bigotry. A lot of people with useful ideas have been bigots. This does not mean we must discard their ideas, nor that we must accept the bigotry. It does mean that we need to critically examine the ideas to see if they are rooted in and/or affected by the bigotry, and if it is possible to effectively remove them from their bigoted origins, or if the bigotry is so wound into the ideas that they is no longer useful if you wish to avoid harming the group the thinker was bigoted against.
This is difficult work to do. It is intellectually intensive, and emotionally exhausting. You will start seeing bigotry in all kinds of places, including media you thought of as "good" and "progressive", and that will also be emotionally exhausting and dispiriting. It will also mean that you are no longer passively absorbing those bigoted ideas because you settled on the idea that this media is "good" and that as long as you only consume "good" media, you will be free of bigoted ideas- a premise that is disturbingly popular for how incorrect it is. Knowing how to recognize and discard bigotry in works is far, far more useful than flatly refusing to consume more overtly bigoted works.
One way to make it easier is to form reading groups, so that you can lean on each other when reading something that's affecting you badly. It also means that there's more than one person processing the bigotry, so other people might notice more subtle parts of the bigotry that slipped past you in your own reading, allowing you to have a fuller picture of the book. If you can't form a reading group, more famous bigoted works often have criticism available online for you to read through. Remember to do your own research. What makes doing this so valuable is increasing your own ability to detect bigotry and to think critically about material you are consuming.
You do not have to limit yourself to traditional media, either. There are forums and social media bubbles that are hotbeds of bubbling, seething bigotry that is more extreme and repugnant than the vast majority of published work. Reading these conversations can be useful for the exact same reasons that reading overtly bigoted books, articles, letters, and essays can be, and they often contain more up to date dogwhistles. However, this is a riskier move. Social media is built to make you keep scrolling, and you can easily find yourself at your wits end and vulnerable to a bigot whose rhetoric is slightly less obvious than the others. In addition, it can be tempting to interact- at which point the bigots will either attack you or try to recruit you, both of which are damaging to you. Only read the conversations of bigots if you are well supported and have strong impulse control, and read them in small doses.
You are not immune to propaganda, but you can partially inoculate yourself into being less vulnerable by consuming it in controlled circumstances that match your ability to recognize it as such and reject it.
