Complex sentence: For many, particularly among the poor, he was seen as a valuable member of the community, although he upsets others, in particular wealthier people, who deemed him to be "a dangerous quack and disseminator of superstitious nonsense".
Split into simpler sentences: For many, particularly among the poor, he was seen as a valuable member of the community. He upset others, in particular wealthier people, who deemed him to be "a dangerous quack and disseminator of superstitious nonsense".