Governments should recognize that the nature of encryption is such that that there will be situations where access to information is not possible, although such situations should be rare.
The assumption that government should be able to weigh in on use of encryption is likely the purpose of this letter, IMO. They are framing the argument by assuming a permission-based situation.
As it stands, you don't need permission to use encryption in communications, and it needn't be rare.
The government of a free people necessarily has its hands tied. This letter is trying to undermine that notion.