Nationals, but not full citizens: Naturalisation policies in Mexico

Despite being citizens, naturalised Mexicans are subjected to large restrictions in their political, civic, and even labour rights. Why such discriminatory regime is applied to such a reduced group of citizens, in a country that officially prides itself as open, tolerant, and having an intrinsically 'mixed' national origin? My hypothesis is that the roots of such differentiated treatment are the ideological legacy of the 'Revolutionary Nationalism' doctrine, which was promoted by the Mexican state during most of the 20th century, and is still expressed in laws and policies.