The historical context is that the Spanish Civil War and the Catholic martyrs here listed should be seen as a whistle stop along the journey from the atrocities against religion of the French Revolution and the murderous repression of religion by the Soviets in their revolution.
It is sobering to contemplate the instinct toward bloody repression of religion contained deep within the left's DNA.
Repression of some religions, that should be. Well, all of them, except for Islam. For some reason, perhaps because it is the perfect theocratic “religion” for a communist state, the left adores Islam.