Don't want to be stupid? You're in luck; you can choose not to be.*
Practice good faith open_in_new.
Learn from multiple sources of reliable information.
Avoid cognitive dissonance.
Have civil conversations ¹
Remember we'll all be dumb from time to time, and that smart habits are hard to form. Stay willing to acknowledge and apologize for your own ignorance, and to forgive that of others.
"It's easier to fool people than to convince them that they have been fooled."