It's very common for project managers to refer to employees as resources. The dictionary definition of resource is something that can be used for support or help. People are people, not things. A chair is a resource. A computer is a resource. A person is not a resource - a person is a person.
By using the term resource, the individuality of people and the value they provide are trivialized. You can swap one similar chair for another, but can you really swap one "similar person" for another?
This may seem like a small thing, but it's really a small thing to start calling people people, and it can make a big difference.