I think one cause of this inability to tolerate dissent is how scientists and capital-S Science have functionally (and inadequately) replaced religion/ethics/philosophy for a sizable portion of society. Many otherwise intelligent people think that religion/philosophy is purely subjective, merely a word game, or not something "serious" people study. Of course, they do this without understanding that this position is itself a philosophical position, the result of centuries of intellectual development.
The result: science, which is supposed to be a neutral process that encourages dissent, becomes a political game, where scientists are treated as the ultimate authority on non-scientific questions.
The result: science, which is supposed to be a neutral process that encourages dissent, becomes a political game, where scientists are treated as the ultimate authority on non-scientific questions.