If you want an exchange with a Tobin Tax, then create one. Everyone who thinks it's a good idea will trade on it. Others won't unless you force them to. We'll then let people figure out how valuable HFT is.
Thanks for your answer, it's a good one, and it makes me think

Maybe that's the way to go, but for that we would need producers/retailers to agree with that, which need pressure from people, which need people to understand economy.
That's why niemivh idea of creating a website is a good one.
Call me an utopist, but I still hope that one day people will get it. We just need good (and not corrupted) teachers, and a motivation for people to understand economy. Perhaps the present economical situation could help with that