The literature you are looking for is regarding group polarisation in the Internet era (with "polarisation" being the main research keyword here).
There are supporters of your idea as well, most notably Eli Pariser (2011) and Cass Sunstein (2001, 2009, 2017) and studies that show polarisation on the Internet. That being said:
However, when comparisons are made between offline and online sources, studies find similar levels of segregation. Figure 1, taken from Gentzkow and Shapiro (2011), shows that segregation across website visits is smaller than segregation across national newspapers, but larger than segregation across local newspapers. Halberstam and Knight (2016) examine political networks on Twitter and find similar levels of segregation in the Twitter political networks as in offline political networks. Furthermore, while suggestive, segregation across information sources on the internet is neither necessary nor sufficient for the internet to increase polarisation.
(Source: "The internet, social media, and political polarisation" - Levi Boxell, 2017
So you are on the right track, your question was thought of before and the keyword "polarisation" might lead your research about it in more depth than this quick answer.