That is true, the Nazi's didn't go after sexual minorities until 1934, but persecutions began for socialists, communists and sexual minorities (as their supporters were largely overlapped) years before that. I mostly have a burr in my britches over Niemöller leaving out other victims of the holocaust like the Roma and what today would be called LBGT+ people. But it's not a competition, the poem's point stands that the Nazis come for everyone eventually because fascist ideology is intrinsically corrosive - it needs a constant threat to justify it's ever-consuming need for power.