While I am unlikely to feel the bite of what is the problem here, I understand why so many are hurt by this issue.
that being said, kickstarter "promises" aren't exactly the best thing to grab on to. Simple as this, if development changes, development changes. Should they have been more specific about this particular decision as soon as they got to it? Yes. Would it have been bad PR? Yes. but honestly, at least they could have been immediately translucent about the online requirement.
Development is tricky, and having a solid vision of what you want for a game is a rarity... And that is something FD most definitely have. their hope was that they could handle most of the galaxy building stuff in a way that both the player client and the server could handle them for their respective modes; but the time they could have spent developing the offline mode was spent on things they felt would be more cohesive to the overall vision for the outcome of the game.
That really does suck for people who don't have a steady internet connection and I hope the quality of the "dynamic universe" that they build instead will really make up for the slap to the PR department and probably a few successful refunds. honestly, if it makes for a stronger overall game, that fits to what the developers want... even if I couldn't play it... it would be selfish for me to ask otherwise. I would just want a refund.
It's not just kickstarter promises - I bought the game from the website 6 weeks ago. it clearly advertised offline solo play as a feature.