Reddit's justification for this is profoundly wrong. Their "public content policy" is absurd doublespeak, and counter to everything the open internet is and hopes to be. You cannot simultaneously call yourself "open" and "public" while refusing access to automated clients. Every client is automated. They even go so far as to say that "crawling" (also known as "downloading") is an "abuse" and violates user privacy.
This is absurd, and not justified. I would love to see legislation that restricted server operators' ability to prohibit automated access in this way, but I suppose it will never happen. Some people in this thread have attempted to justify the policy by saying "they have to protect their income streams". No they don't. You don't have a right to an income stream, and you certainly don't have a right to lie in order to get all the benefits of an open internet with none of the downsides. Noting of course that the "downsides" are in this case actually just "competitors".