I don't see a mention of "immoral", but there are certain people you don't want to give upload rights to: people who will introduce backdoors, people who will be irresponsible with their private key and leave it lying around in public places, etc.

The ability to include code in a release of widely-used software involves a large amount of trust, and for a distributed, volunteer project, you don't get the checks that either a long personal relationship or a formal employment background check would give you. This puts you at risk of, as Juniper so eloquently put it recently, "unauthorized code".