A agree with you that the "security" spiel does get increasingly annoying. However, as it has been said, there is a reality, which may or may not affect your environment.
There are also weaknesses in the textbooks, particularly running executables from a link in the document.
If the text books were created by your organization, you would have some possibilities to make them less an issue, although there may or even will be side effects, which have to be taken into consideration:
• Making the textbooks into Portfolios, where all the subsequent documents are included. This would allow to access those documents without having to do an external link.
Hope this can help.