I am not an expert on this either, though I guess I hope to be someday. But when Hossenfelder says that Spin-2 necessitates like charges attracting, I believe her. I've also heard that result elsewhere.
My understanding is that the spin of a field or particle is more of a result of the equation (specifically, the Lagrangian) which governs its dynamics. This is irrespective of whether you consider it as a field or as a quantized particle of that field; either way the Lagrangian has certain symmetries. The Fermion Lagrangian has symmetry on 4pi rotation, but not 2pi, which (confusingly) we call spin-1/2. I suppose that the GR Lagrangian has symmetry under pi rotations, which corresponds to spin-2.
(that would make sense if the stress-energy tensor is contracted with two vectors; it would essentially boil down to the fact that (-x^T) M (-x) = x^T M x if you wrote everything as matrices. But while I have studied GR I haven't studied it as a field theory so I'm not sure it's this simple.)
So the Spin-2 thing is not too questionable. I don't anything about how to turn that into a statement about gravitational charges, though.
