Here's the thing those politicians do not understand: It is possible for anyone to employ secure, effectively unbreakable, encryption. If one is about to do serious crime, any law to require 'breakable encryption' will be a lesser one to break, so the criminal does not care about that.
Hence, you as a politician CANNOT make an argument that such a law is required in order to fight crime. It won't work. The ones you argue to try to catch you WILL NOT be able to catch this way. You DO NOT have a rational argument for it. The math for such encryption is out there. The genie's out of the bottle.
Stop using this argument. Stop demanding the impossible.
Because, if you do not stop to make that argument, you either reveal yourself to be ignorant, or evil/autocratic/dictatorial/un-democratic.