Let $L$ be the Banach algebra of $L^1$-functions from $\mathbb{R}$ to $\mathbb{C}$ with $L^1$-norm and convolution as algebra multiplication. Assume that we knew that the homomorphisms from $L$ to $\mathbb{C}$ are the zero map and evaluation of the Fourier transform at individual real numbers: $f \mapsto \int_{\mathbb R} f(t)e^{it\alpha}dt$ for some real $\alpha$. We may add a unit $e$ to $L$ artificially by considering the new Banach algebra $A:=L\oplus \mathbb{C}\cdot e$ with natural operations. Then the fact that any $L^1$-function whose Fourier transform is zero must be zero itself may be rephrased algebraically: the algebra $A$ is semisimple (as maximal ideals of unital Banach algebras correspond to homomorphisms to $\mathbb{C}$ by the Gelfand-Mazur theorem).

My question is whether this may be proved a priori and independently (and maybe for some wide class of commutative unital Banach algebras).