The stranger had crossed a sacred line. He had mentioned the men's mothers. Nothing could get him out of a beating now, even the fact that he was obviously a simpleton. Albeit a simpleton with a good vocabulary.
disapproval If you call someone a simpleton, you think they are easily deceived or not very intelligent. `But Ian's such a simpleton', she laughed. someone who has a very low level of intelligence (simple + -ton (probably as in names like Washington))