I think the best "point" to make to them here is no point at all. That is to say, you don't approach it as ignorance to answer with knowledge, you use the socratic method on them, or to put it another way: you revert to being a small child and keep asking "why?"

I'm being a bit tongue in cheek on that last bit, but I am serious about the general idea. At this level of ignorance, you can waste a lot of time trying to "teach" before even knowing what it is exactly that the person believes. So it can be much more productive to ask, i.e. stuff like, "why do you think he's a communist?" or "what does communism mean to you?"

fictional example to illustrate: "what does communism mean to you?" "it's when the deep state controls everyone" "what is the deep state?" "the deep state is those people in the shadows who control everyone" "who are the people in the shadows?" "well I don't know, they're in the shadows" "so how do you know they're connected to Trump?" "because he says communistic, deep state stuff" "like what?"

and so on. Of course, it's possible the person loses patience with you or whatnot, but I think people are usually more open to explaining themselves than being explained to, unless they're in it to learn. And someone who believes such an absurdly disjointed political thing about Trump is probably not going in headfirst with an open mind. In general, the idea is not only to better understanding what it is the person believes, it's to effectively confront the person with their own beliefs and any contradictions within them. It's something I recommend to be used sparingly cause you can definitely be a very annoying person if you use this approach as a way to avoid ever presenting and defending your own positions, but it has its uses.