Answer: Because they have to create the perfect race, anyone who was considered a threat to this plan should be exterminated. In their minds, some groups were specific threats.
Explanation:
Hitler, and all your guards, thought that people of some specific kind, like Christians or Jews, for example, were not of a perfect race, so he would send them to concentration camps to maliciously kill them.
In addition to being racist, they were sexist too or just didn't like a certain group of people, that's the reason why they would target different types of people, like women, twins, homosexual, etc.
