That is a symptom, not a cause. That means education system is bad and has failed people, OR, that people are so desperate with their living standards that they're not disinformed but they just want to take revenge on the establishment that has failed them by voting extremes.
Either way, those are symptoms, not the cause so I don't believe government enforced censorship is the solution because that's exactly what totalitarian regimes did when people were unhappy. The solution is for the establishment to accept they have failed the people and start to do good for the people or step down.
This means the democratic system IS working as intended, as if you were to censor speech and take away peoples' only legal way of protesting (voting), then their next alternatives is violence and uprising.