True this needs to be solved.
Still, Monero is just a crude hack compared to zerocash.
You are assuming that it can be solved. I am skeptical.
Have you read the rest of the Zerocash paper and process? The crypto is seriously cutting edge. I'm educated quite highly in related areas and I can only understand at a higher abstraction level what they are doing. Zero-knowledge proof is very impressive. I'm sure they'll be able to leverage something similar to solve this issue.
I'm not picking a fight. In fact, Monero is the only altcoin I have any stake in at all at the moment. I sold all my peercoin and litecoin months ago at the peak (whcih was mostly luck). I'm merely trying to poke people so I can find out whether there are more and better arguments now for Monero to "win". If people would convince me better I might increase my stake in Monero (current prices while low are still substantially higher than when i bought the Monero I currently own).
I dunno I have some training in this area as well and see things somewhat oppositely to you. If someone wanted to trust their real money to something I made in grad school I would raise my eyebrow pretty highly. I have no doubt that the work that Matt Green et al. are doing is academically intriguing but the fact that it is cutting edge and unvalidated by the academic cryptography community is not really a strength. Ring signatures are a well-validated cryptographic approach with a strong literature base supporting them as an elegant and reasonably secure approach to privacy.