All too complicated
The simple issue is that if the government mandates a backdoor then at some point a criminal will obtain it - and then have access to everything. Just knowing that it possibly exists will concentrate the minds of many people wonderfully.
Despite all the efforts, the secrets of building nuclear and thermonuclear bombs could not be contained, as a result of which we have Israel, Pakistan and India with enough nukes to wipe out the Northern Hemisphere (The Russians might have been able to develop them independently as soon as they knew they were possible, but the help must have saved a lot of time). Snowden was a comparative amateur; imagine a Philby in the NSA. Even the nicest, most democratic government in the best of all possible worlds is not safe with backdoors because they can be stolen. Clinton obviously doesn't get this point because, like most people in Washington and London, she cannot imagine people other than the carefully curated set of people that she meets.
Biting the hand that feeds IT
