«لَقَدْ جِئْتُمْ شَيْئًا إِدًّا»
You have uttered something gravely objectionable.
Laqad strengthens the assertion; iddan describes something shocking or grave. The elder opens not with a gentle qualification but with a forceful rejection of the group’s verdict.
His argument is that reverence for great writers of the past does not justify dismissing all ability among people now living. The intensity of the sentence introduces a dispute about standards of judgment, not merely about personal preference.