How do the nuns who ran these laundries reconcile their Christian principles of love, forgiveness, not judging with what went on inside them
They don't have Christian principles, they have RC ones and these are different.
The laundries existed in England too, not as many, but they existed.
Look at Mother Theresa, she got the Nobel Peace Prize and is on her way to being a saint. From an RC principle she did wonderful things. She created a home for the dying and ensured as many people as possible died as RCs.
But then take a step back and look at what she didn't do. Anyone entering the home was there to die, even though they could be treated and live. Life saving treatment wasn't offered, in fact it was (and I assume is) with held.
In her acceptance speech for the NPP she talked about teaching 'natural contraception' to leppars. Leprosy is completely curable. The WHO has also made it free anywhere in the world.
What sort of person encounters someone with a disfiguring and disabling disease, that can be cured, and does not tell them where and how to get treatment?
Well someone that thinks suffering is good for you, and that it will get you a place in heaven may well think it is in your best interests to remain in suffering.
My dad is cradle RC, my mum is a convert and I spent most of my schooling in RC schools.
There are certain things my mother just does not 'get', that my upbringing means I do. I do not think this is right, just that I understand the reasoning.
Eg my mum heard about a woman who's ultrasound scan showed serious disability. Being a good RC woman she continued her pregnancy and then after the birth came home leaving the baby in hospital.
My mother could not understand how a woman could give birth to a child and then try to pretend nothing had happened.
My RC schooling taught me she had done all she needed in giving birth. That's all the RC church asks for.
Added to this warped attitude is the idea of serving 'penance' on earth. So when you became a nun you were asked about your interests and likes and were then sent to work in something you didn't like. So if you liked working with old people and hated children you may well find yourself in a nursery or a school.
My old headmistress was quite clear that she had never wanted to be a teacher but that is what the convent told her to do. They also sent her from the Republic of Ireland to Belfast to train, then to England to teach.
Having said all that, I know lots of people who attend RC churches and do not have the same mentality, I hope it is on the wane.