If they genuinely believed in the moral excellence of burglary, penal servitude would simply mean so many happy years for them; all martyrs are happy, because their conduct and their principles agree.

That sounds all deep and wise... until you observe that it seems to be an arbitrary redefinition of 'happy', redefinition of 'genuinely believe in the moral excellence' or blatantly wrong as a matter of fact. The accuracy of the claim doesn't seem to be an important part of the intent, that is, it is bullshit.

Other parts of the excerpt are not bad - that part is just a point that people often try to take too far. The benefits of internal coherence and happiness are not tautological. Not even close.