A Kibbutz is typically very leftist, it is a commune after all. They probably would not arm themselves even if they were ordered to do so. Israeli Jews are not conservative when it comes to social issues.
Not all kibbutzim are leftist. Some are religious. But even if they were leftist, there is no doubt they loved their children. I cannot imagine what went through the mind of the Israeli soldiers who discovered this horror. I know I would have collapsed in grief.