posts and reposts were filled with hate, referring to jews as "the children of satan" and both jews and muslims as "filthy" and "evil." his posts were on gab.com which bills himself as a haven for free speech, but critics say it is a gathering place for white nationalists and neo-nazis. additional sites like 4chan, 8chan, and reddit also draw racist and anti-semitic rants. george selim, with the anti- defamation league, said his group alone monitors dozens of social media platforms and hundreds of sites. >> various online platforms have ccome the mechanism of choice for individuals to share and disseminate vitriolic, anti- semitic propaganda. >> reporter: most of bowers' comments were protected by the first amendment, until he appeared to incite violence just hours before the attack, saying, "screw your optics, i'm going in." both local and federal law enforcement agencies work with companies like facebook and twitter to flag any speech which poses a threat.