The legal theorist is only talking about individual people and their private diaries. Interoffice memos are not analogous to diaries. Diaries are a private conversation with oneself, while interoffice memos are shared throughout an office.

The legal theorist is advocating for a specific restriction on admissible evidence used in government investigations, while (B) supports loosening some of these restrictions. (B) also fails to address why a person’s private words shouldn’t be used against them.

This suggests that governments should never use a person’s words against them if those words were meant only for the person herself. This supports the idea that the government shouldn’t use someone’s diary as evidence against them.

The legal theorist is discussing words directed to oneself, whether spoken or written. Correspondence isn’t analogous to a private diary because it’s between two or more people.

This weakens the argument because the legal theorist wants to limit what governments can do in investigations, while (E) argues that governments should do everything in their power. Presumably “everything” includes using someone’s personal diary against them.