Demos are flat out one of the worst and retarded mechanics in the game for the simple reason that there is so little counterplay to them, and that they can decide the game in one fell swoop for 90 munis, and I say that as a fanatical demo user.
We do have counter play for Demos, minesweepers. This might sounds odd, Whermacht/OKW has to adjust their strategy with infantry pushes supported via mine sweepers. CAS has no counter play what so ever, but that is another topic.