I don't know how to put this delicately, but:

1.) I grew up in this line of thinking (but also deeply religious, so it's a little different) and it dissipated due to two main things: psychedelics and losing weight/becoming more confident and in-shape. In my case, I hated myself because I was unattractive and very overweight. I saw other people getting girls and resented how easy it seemed, while I felt invisible.

2.) Much of my family is like this and it is always due to a similar lack of confidence/self-loathing.

I'm not suggesting anything, just throwing it out there. That's a hard thing to "gift" around, if it's even at all potentially relevant. Gym membership or weights? You'd have to have a pretty unique relationship with your son to give him psychedelics or a trip to a nice strip club, and I'm not even sure that solves anything necessarily (just using it as an extreme example). Could be badass. Could be really weird/icky. Probably the latter. Massage is less weird? I don't know.

Which is why I agree with the sentiment of separating it all from Christmas and just love him and give him something that shows you know him and know what he would like, so that he feels seen and appreciated. "I'm not going anywhere" is the most-powerful message you can try to send. I'd say IF you try to gift something like that, make sure it's only a side item. Don't make the entire thing about your differences.

Many cliches of parenting turn out to be realities as you go. You find yourself realizing tropes exist for a reason. They grow up fast. Different phases at different periods. Moody teenagers. They're not always true, but they often turn out to be understandable. Besides the above, it's worth considering whether there might be some element of "rebellion" in it, if he grew up liberal. Maybe it's just "doing the opposite of my lame family," like a little bit of a "fuck you, dad!!!" phase? No matter what, you lose the more you dramatically respond. I think riding it out by being the rock who loves him no matter what is ultimately the best play, which means some awesome gift that he would love.

Coal. For some reason Republicans love that stuff.

A Peoples History of the United States by Howard Zinn

I would say, a good conversation. Listen to him, ask question, don't be too judgemental (and that can be hard). But also accept, that for a big part, you can't form/force his way of thinking. In the end he has to find his own way in life.

Start with video games. But try to make it a game that has couch co-op so your family can come together.

The more you try to overtly meddle the more the kid will be convinced of their beliefs, reactionaries thrive off disagreement and arguments.

Get them something normal, perhaps something the connects with nature. Your goal should be to get them to connect with you and the rest of the family, you want them too feel like they are part of the in-group.

I used to be heading down this path as a teenager. For me, college was the eye opener. When I broke away from my normal bubble of people, I would have my opinions and biases challenged.

I like the travel suggestion as well. Also I went to some music festivals around that time that were pretty significant to my beliefs. I guess it depends on the type of music they prefer though.

An education?

I'm not joking or kidding or insincere. I actually don't know what to do.

The Jungle, by Upton Sinclair.

Some political theory, then read it yourself so you can stop being a liberal /j

We really need better terms than facist or nazi. People keep confusing the meaning of the words because its all we have for description of this thoughtset. There might be some overlap, but unless it 100% fits it just creates opportunities for people to be confused and issue to get muddied by pointless arguments and misunderstandings.

For some time i have thought this type of thoughtset as "dark humanity", but i'm not sure how fitting term it is and it feels kind of over dramatic. It just feels like humans are fundamendally split about one or more core issues, with some in the middle too. Though i'm also worried that making such clear distinction would also make the separation more solid. The issues also need more defining.

Why we need better terms is that we need to be able to confront these people without insulting them as first thing, otherwise we are just aiding the enemy by pushing them further in. Calling someone nazi or facist only hurts if there is any chance to save them. Its no better than calling someone libtard.

Das Kapital

Coal

does he like music? see if theres any old punk shows around or any records/vinyls if he likes that at all. sex pistols, dead kennedys, hell, even green day.

I don't know how else to show him I love him or that he's a part of this family.