This is what helped for me for years: I stopped having discussions regarding opinions based on fake news. I usually just tell them that I don't have an opinion on the matter and that I don't care what their opinion is. I prefer to talk about something else.
In my opinion, I think it's better not to have too many opinions in general. This is one of the few opinions I have. It seems like our brain wants to have opinions on everything. But often the topics we want to have an opinion on are much more complex than we might think they are. To form a good opinion on the topic you must be able to understand a lot of the ins and outs of the topic. That takes a lot of effort. This is what fake news (and probably also correct news) abuses. It tries to form an over-hasty, sometimes completely wrong, opinion on a topic that's very complex to understand. Most people don't take the time to understand the complexity of the topic, and therefore think that this fake news opinion is the correct opinion. For most it takes too much effort to understand exactly how it works to realize that their opinion is not correct. Or even worse, there are many topics that probably don't have a correct opinion: are their more universes, what will the weather be in 10 years, will the stock market go up or down next year? Nobody can tell, even not the experts. I think that the only way to win the argument, is not participating. Just let it pass and let the experts (who have spend their whole life on it) deal with the issue.
For example, do you understand how mRNA vaccines work? How mRNA is transferred in lipi nanoparticles where ribosomes produce viral antigens? How cytotoxic T cells and T helper cells bind to the secretory vesicles to create a viral response? I sure know that I don't understand it, and it will take me months, maybe years, of deliberate practice to understand how mRNA vaccines works. I probably need a PhD in adaptive immune systems to understand this topic completely and for a good opinion. So I decide not to form an opinion about it. I trust the experts, who spend their whole life working on mRNA vaccines, to be right. If someone else has the opinion that mRNA vaccines don't work or are dangerous, fine, they can have their opinion. It's good to be (self-)critical sometimes. But I'm not in a position to argue with them, because I'm not an expert on the matter, nor do I have the time and (probably) the brains to understand this complex topic completely.