You are not safe from this. You, the person reading this, are not safe from this. No matter how educated or open minded you think you are, you are not safe from this. The moment you think you are safe from it is the moment you become the most susceptible.
Its similar to why you cannot put bad people in a class of their own. The moment you do that you stop being able to see the bad things that the people closest to you do a la "my best friend couldn't have said that racist thing, they're not evil."
The moment you think you are immune from this type of backslide into right wing nonsense is the moment you stop questioning yourself enough to keep yourself from backsliding into right wing nonsense a la "I mean im not antiscience, im vaccinated, I just think that fluoride in our water supply is imparting children's ability to learn as fast as they otherwise could without it."
Remember, being progressive means progressing, its about always moving forward. The moment you rest on your laurels and stop putting in effort to keep the progression is the moment you start becoming left behind.