If you ban Bitcoin, then Bitcoin will become forbidden fruit and people will want it even more in my opinion. This will just give a sign to the world that we are doing the right thing.
Not that I think a ban will ever happen, but who would want a form of money that can't be spent or accepted? Bitcoin isn't drugs. It's not fun or addictive or profitable regardless of legality. It serves a purpose. Banning it stifles that purpose and people will move on. They're not short of alternatives right now.