The underlying logic is that capital would shift from bond to equity markets, and while that's perhaps a little oversimplified I think the point is still valid. A bond market crash would trigger a risk off move [1] in which safe haven assets such as gold, the dollar, and in fact government bonds would outperform while risk assets such as equities are generally sold.

[1] http://lexicon.ft.com/Term?term=risk-on,-risk-off