This thread seems to have lost its way somewhat.
Why is rolling G dangerous was the original question?
I believe tha answer comes from the fact that aircraft are designed to have certain margins for structural strength, with that design come certain "assumptions" about how the pilots will make inputs - in general this includes a certain amount of symmetry, or single axis inputs particularly at the extremes of Gz. If the designer chappie had to account for maximum roll rates being applied at maximum pulling g then the fuselage would have to be extremely strong to cater for the torsional stresses developed between wing and tail. Basically to stop the tail from falling off!!
As an example an F-15 was quite happy at 9g in a straight pull, but a twitch of roll would trigger an "over g" warning.
There are a couple of solutions: make the fuselage stronger = excess weight for the whole life of the aircraft to cater for a small region. Tell the pilot not to pull and roll = fine in the "good old days" but subject to human failings. The ideal solution, is to incorporate appropriate scheduling into the flight control system either by limiting the roll rate at high g or reducing the demanded g when a large or abrupt roll input is made.
Makes any sense?
T