Taking that line of thought further, that means if bonds and stocks are both down, then cash is a good place to be...when inflation is up? Investing is hard.
Of course, real decisions are made on figures. The actual way of making this decision would be to compare the bond yield with the expected inflation. If expected inflation is higher than the bonds yields I'm going to sell my bonds for cash and so will a lot of people, so the bonds price will drop and the yields will raise until a point where they're attractive again.
But yes, it is hard.