Proton is a spin-1/2 particle but composite i.e., it's a bound state of three quarks. Protons have partner called anti-proton which is also composite. Is it not a Dirac fermion? If not, why? In other words, why should a Dirac fermion always be elementary such as electron, positron or neutrino?
By Dirac fermion, I understand a quantum of the Dirac field and which also has a antiparticle partner. If it's a Dirac particle, does it mean protons also have Lange-g factor $g=2$ like an electron (apart from the anomalous contribution)?