I think his post is nothing to do with the match between Barcelona vs Real Madrid. It is true that Barcelona is dominating group H, they always win every match and be the leader of group H now. It is very obvious that Barcelona performance in UCL looks impressive so far. However, it is still in group phase, we don't know how Barcelona can maintain the good form when the group phase is over (knockout phase).
I don't want to conclude how far Barcelona to compete in UCL based on the result on La Liga. Sometimes, the performance in UCL and local competition can be different or contradictory (opposite). Although Barcelona looks dropping their performance in La Liga, how knows if they can play better in UCL.
It all depends on who they meet at the 1/8 final stage. At the moment, Barcelona have average results - in La Liga they have drawn three times with weak teams and once lost the game to a strong team (Real Madrid). With no other big games Barcelona have had this season, it was hard to tell how good or bad they were overall. But if at the 1/8 stage they come across someone strong, then I am sure that Barcelona will be the underdog.