Poincar\'e inequality 3/2 on the Hamming cube

For any $n \geq 1$, and any $f :\{-1,1\}^{n} \to \mathbb{R}$ we have $\Re\, \mathbb{E}\, (f + i\, |\nabla f|)^{3/2} \leq \Re\, (\mathbb{E}f)^{3/2},$ where $z^{3/2}$ for $z=x+iy$ is taken with principal branch and $\Re$ denotes the real part.