This is why the scientific method is a robust process. When bad theories are investigated, the unyeildimg accumulation of evidence will eventually result in an improving model of objective reality regardless of individual idiosyncrasies.
Just like journalists, scientists can select which ideas to research, which ideas to promote, which ideas get funded, etc.
So if all of science comes from people with one homogeneous ideology, you're going to get homogeneous ideological research.