I have followed Rubio for many years now, and he really really hates Communism.
That sort of frothing at the mouth hatred dating from the Joe McCarthy time. No objectivity, just hates it.
Now, I am not keen on communism. And for a while I did sort of respect his position, but wow, that respect vanished when I started to see how irrational his hatred of it is. Likes of Ian Duncan Smith is much more balanced and worthy of respect on that issue than Rubio is.
When I had Twitter, I followed him and he would post Bible verses every day. I am sure he is old school evangelical. Communism is atheist so is therefore the devil.
My guess is he looks upon the suffering of the people as him trying to save their souls. Mother Teresa style. And I can't find what he said on the subject of the death sentence (he is blocked where I am), but I recall that he is in the school that says the death sentence is good because the condemned nearly all find God and repent while on death row. So, executing them is saving them.