“I would say that in the spreading of misinformation, online confirmation bias is the driver,” said the study’s senior author, Walter Quattrociocchi of the IMT Institute for Advanced Studies in Lucca, Italy. Confirmation bias is the tendency of individuals to pay attention to or believe information that confirms the personal values and beliefs they already hold, rather than allowing their beliefs to be changed by new information … Sociologists have suggested that the reason has to do with the fact that it’s difficult to change an individual’s worldview simply by presenting new information. Confirmation bias, rather, leads people to seek out evidence — however small or poorly supported — that supports their existing personal beliefs.

https://www.washingtonpost.com/news/energy-environment/wp/2016/01/04/heres-how-scientific-misinformation-such-as-climate-doubt-spreads-through-social-media/

Users tend to aggregate in communities of interest, which causes reinforcement and fosters confirmation bias, segregation,
and polarization. This comes at the expense of the quality of the information and leads to proliferation of biased narratives
fomented by unsubstantiated rumors, mistrust, and paranoia.

http://www.pnas.org/content/early/2016/01/02/1517441113.full.pdf

Further readings:

(1958). Traité de l’argumentation: La nouvelle rhétorique. Paris: Presses Universitaires de France