I wouldn’t offer to teach critical thinking skills, that would be ridiculous. Instead, I would probe with questions and get them look at what they were posting more clearly or refer back to actual sources.
I also said it was a fools errand - something that had little chance of succeeding against the waves of misinformation on Twitter. And finally, you’re right that knowing you can be wrong and challenging your own beliefs is fundamental to critical thinking.
I think that's fair. The internet is full of people who won't even go to the effort of reading the article they are confidently promoting as the truth. Sometimes something as simple as "actually this study is about lions. not people" is enough to bust some people's bubbles.
I also said it was a fools errand - something that had little chance of succeeding against the waves of misinformation on Twitter. And finally, you’re right that knowing you can be wrong and challenging your own beliefs is fundamental to critical thinking.