rw [← coe_inj, coe_smul_finset, coe_mulStab hs, Subgroup.smul_coe ha]
case inr
ι : Type u_1
α : Type u_2
inst✝¹ : Group α
inst✝ : DecidableEq α
s t : Finset α
a : α
ha : a ∈ stabilizer α s
hs : s.Nonempty
⊢ a • s.mulStab = s.mulStab
no goals