If you watch closely, you will see the person being invalidated flinch, withdraw, or become defensive. It is abusive, and it occurs outside of most people’s consciousness. He will feel emotions, be afraid of them, and repress them.
Most individuals don’t know that they are causing harm. A 3-year old boy is crying because he skinned his elbow falling off his tricycle. The girl that was interested in him will find him cold, aloof and emotionally unavailable. This pattern repeats itself in adulthood, leading to Dad, the three-year-old 20 years ago, now telling his boy to man up and stop being a sissy.
When people say that relationships take work, they mean maintaining that constant balance of each other's emotions.
Your partner avoiding the "work" in the relationship is like wanting to have his cake and eat it, too.
Invalidation, as used in psychology, is a term most associated with Dialectical Behavior Therapy and Marsha Linehan.