This paper discusses the phenomenon of radicalization into online conversation, especially through social network sites. Then, we analyze comments posted by Facebook users on Brazilian newspapers' fan pages on that social medium. 628,057 comments mentioning at least one of the main candidates during the campaign were classified. The article discusses some aspects of radicalization, so it analyzes two specific variables: reflexivity and form of comments. Results show that social media, even though they open a space for dialog, give place to debates in which participants prioritize criticism or praise for candidates, and they basically lead to persuasion and radicalization. [ABSTRACT FROM AUTHOR]