1) It means that someone suggested to Mr Al Faed that he (Mr Al Faed) thought that anyone who disagreed with him must be dishonest. Note that, for me, there should be no comma after "him" but there should be a comma after "was" and after "mind".
2) It should be "steel" not "steal". It suggests to me that the Security Services have some proof which could help Mr Al Faed's case but they have erected a (metaphorical) wall which is so strong that he cannot get through it to reach the proof he needs.
Student or Learner