Cali Williams Yost's Answer:
Here's the funniest part of what happened to you. Your manager's response makes perfect sense to him. He thinks, "If I say no, then he'll quietly go back to working the way I want him to, in the office, full-time, everyday." But what he actually said without realizing it was, "You're too valuable to me, so you need to leave."
This is a huge roadblock for managers, especially those without experience managing flexibility. Before a discussion about a flexible arrangement, they need to realize that just because they, as the manager, would prefer someone work a particular way, it doesn't mean that person can or wants to. And saying "no," won't make that person forget about the whole crazy "flex" thing.
If someone like you is motivated enough to present a proposal, chances are they are also motivated enough to make a change (e.g. find a new job) if they don't get at least some version of what they present for at least a trial period.
Consider your manager's response a compliment, albeit somewhat backhanded and misguided. Take the knowledge of your value and use it as leverage to restart the conversation. In a very non-threatening way, point out that you hope the two of you can come to some agreement on your proposal because it's very important to you. And, calmly tell him or her that if you can't, then you may have to consider alternatives that would give you more of the flexibility that you need.
Once the reality that you might leave without more flexibility sets in, you will be pleasantly surprised how fast your negotiation restarts. Be patient, and emphasize that even though you will not be physically in the office a couple of days a week, you will still get your work done. And set a review date in six months to sit down and review how your new arrangement is working. Good luck!