Not only that, but:

Initially, three U.S. servicemen who had tried to halt the massacre and rescue hiding civilians were shunned, and even denounced as traitors by several U.S. congressmen, including Mendel Rivers (D–SC), Chairman of the House Armed Services Committee.

What's in Wikipedia doesn't match my memory; what I thought had happened was that Thompson did more than "try to halt." He landed his helicopter between US troops and a group of obviously harmless villagers and told his men to shoot the Americans if they tried to continue murdering the villagers.

He and the other soldiers who stopped the massacre and reported what had happened were viewed by most Americans as traitors at the time, and for quite a while after.