I dislike having to write this to someone who has written such a kind and touching post asking that errors within a group be corrected, but this group, if it really holds these beliefs, is not a group of Muslims. This is disbelief by consensus. So is this, unless what is meant is a very roundabout thing that I can't possibly infer from this statement. These two fold into each other but I am not certain of the Hukm in this case. The first two are very clear cut. Denying ijmaa' as a concept is massively problematic. Quite bizarre... If this includes things that are haram by consensus or clear nusus, then this is also kufr. The former is Qur'anism and that is kufr, and the latter is extreme kufr... Extremely bizarre. Bwuh? If you've accurately rendered the beliefs of some of these people, then it is not permissible for you or for anyone to give them Salaams, or pray behind them... I'm sorry to say this, but it is worse than simple deviance.