I too no longer preach kindness and inclusivity. I used to, then as the writer says "I fed my child to a lion".
My DS2 is the sweetest child. At his new school he was excluded by parents manipulating friendships. This ended but then he went through 2 years of bullying about his weight and was called "fat and ugly" by one child. This ended up with DS not eating, weighing himself, having body image issues and being really down. The school did nothing until I lost it and only then did very little.
In the end I managed to turn my sons confidence around and gave him permission to stand up for himself whatever the consequences as I would deal with them. I told him to tackle unkindness with unkindness back.
Over the years I've been handed loads of excuses about bullies not having a good home life, not happy etc. Most of the time this was an excuse. Some kids are just not very nice and turn out to be not very nice people. Let's stop making excuses for everything and call it out when we see it. Behaviour is deteriorating in our schools and society. There is not a positive correlation from being kind and inclusive to everyone and better behaviour. Its just a PC bullshit exercise. Often including one person (e.g. a bully) means a handful of other people become excluded such as children who will avoid hanging out with others around them, going to parties and even leaving the school which I have seen many times.