Any communication that separates us from ourselves or other people doesn't work because it ultimately doesn't support the relationship or our ability to meet our needs in our relationship. In Nonviolent Communication, we call such communication patterns life-alienating communication.
Life-alienating communication has a few distinct categories. They are:

Moralistic Judgments
Moralistic judgments imply wrongness or badness on the part of people who don't act in harmony with our values. It could also include anything that involves blame, insults, put downs, labels, criticisms, or diagnoses.

The following are examples of moralistic judgments:
"I think you don't care about me." - Accusation.
"That suit is so ugly!" - Judging.
"He's a micro-manager" - Labeling.
"I would have been on time but this jerk pulled out in front of me and drove 5 miles below the speak limit" - Blaming.
"It wouldn't have been so difficult for you if you'd read the book first!" - Criticizing.

In each case, the speaker is making a moralistic judgment about the other person that implies that there is something wrong with the other person or their behaviors. When this happens, we experience separation because someone is deemed right and someone wrong. The speaker has successfully created a situation that limits our possibilities for connection or resolution.

Making Comparisons
Whenever we compare ourselves to others, we set ourselves up for pain and disappointment. Consider how you feel when you see models in magazines, or when you hear that someone at work is more talented than you are.

Here are a few more examples of how comparisons can separate people:
"You're not half as smart as your sister."
"He's the worst boss I've ever had."
"She's beautiful but dumb as a post."
"I could never draw as well as you do."

Any kind of comparison can generate pain in us and even sometimes pain in the other person. It doesn't matter if you are comparing your skills to a coworker's skill, your spouse's playfulness to yours, or someone else's intelligence with yours. Nor does it matter if you think you are better or worse than the other person - either way you will feel the pain from the separation your comparisons create.

Denial of Responsibility
Whenever we don't take responsibility for our choices, actions and thoughts, or when we blame others for our decisions or feelings, we create separation in our relationships. We are literally denying our responsibility. It is sometimes very difficult to spot when we are denying our responsibility because we are so used to blaming our circumstances on others, and in many cases it seems justified to us.

The following are a few examples of denial of responsibility:

"I yelled at my secretary because she didn't type my report on time." - Blaming actions on the secretary rather than taking responsibility for his actions.
"I cleaned up my office because it was necessary." - Vague, impersonal response that doesn't clarify the true motivation.
"I didn't call back because I was too busy." - It's not that we're too busy, it's that we prioritize our time in certain ways that don't always allow time to return all our calls.
"I lied to the customer because my boss told me to." - Denying responsibility by placing responsibility on a third party.
"I told the customer that they couldn't see their report because it's company policy." - Denying the motivation for following company policy and instead placing the blame on an inanimate object - company policy.

Whenever we put something or someone else, such as the law, our mother, our partner, policy, etc., between us and another person we place a barrier between us. I always feel more reassured and relaxed when I hear someone take responsibility for their behaviors. I might not like the result, but I feel more connected to the person.

An explicit or implicit demand threatens the listener with blame or punishment if she fails to comply with our wishes. Under these circumstances, the listener's only choices are to submit or rebel. Demands, then, actually limit the possibility for connection with the other person and your opportunities for success in your relationships.

Some examples of demands are:
"I need you to take the garbage out tonight."
"You have to be home by 5:00."
Sometimes a demand is disguised as a request, such as:
"Would you like to go dancing tonight?"
"Would you like to help me clean the garage?"

You know it's a demand when you say "no" to the request and then experience negative repercussions.

In summary, life-alienating communication are expressions that separate or distance us from other people. Most forms of life-alienating communication can be found in one of four categories:

1. Moralistic judgments (deciding good/bad, right/wrong, labeling, criticizing or blaming).
2. Making comparisons (comparing ourselves to anyone for any reason, or comparing other people).
3. Denial of responsibility (not taking responsibility for our actions and feelings, thereby putting a third party between us and other people).
4. Demands (making demands of other people which leaves the listener with only two choices, to succumb to our wishes or to rebel against them).