  We extend a systolic inequality of Guth for Riemannian manifolds of maximal
$\mathbb{Z}_2$ cup-length to piecewise Riemannian complexes of dimension 2. As
a consequence we improve the previous best universal lower bound for the
systolic area of groups for a large class of groups, including free abelian and
surface groups, most of irreducible 3-manifold groups, non-free Artin groups
and Coxeter groups (or more generally), groups containing an element of order
2.
