唇舌

I feel like I’m just wasting my breath trying to explain things to him.

我觉得跟他解释简直是白费唇舌。

Those who protested against the president's decision were actually barking at the moon, since they were in a powerless minority.

他软弱无力的少数, 他反对总统的决定际上枉费唇舌。