There was obviously a plenty of very real violence by GC, anyone watching the live streams saw this for themselves.
And a few days ago el pais fired a bunch of folks for having the wrong opinions on Catalonia, so I'm not sure if they're the best source.
https://elpais.com/elpais/2017/09/25/inenglish/1506323273_06...
https://politica.elpais.com/politica/2017/10/20/aixo_va_de_d...
El Pais & Co. are heavily pushing this lie that there's somehow a very significant amount of "fake news" on the other side.
I believe that they are purposefully overstating the significance of the "fake news" on the pro-independence side, and are simply trying to use the slightest indication of such to discredit the pro-independence side as a whole.
Where their theory really falls apart the most is the fact that all the "fake news" they speak of are in English. It feels fundamentally strange that "fake news" on small English language blogs would significantly affect the political sentiments in Catalonia.