To bounce off usually means to rebound (as like a ball does if you hit into a fixed object - it hits the object and then bounces back at you or bounces off in some other direction depending on the angle of impact).

However, in this case, I think the sense is more one of "esbarrar", i.e.: human beings may be asked to stop their inquiries because attaining knowledge is impossible in that area, however, asking humans not to want to know goes again what S called our need to know.

HTH