2 handed backhand is offensive and one handed BH is defensive in case you don't know
If we're talking topspin, then you're wrong.
It's harder to defend and easier to attack with 1 handed topspin.
It's easier to defend (more consistent) and harder to attack (less power) with 2 handed topspin.
Admittedly 1 handers tend to slice more, which is usually used defensively.