Defacing the Humble Stone

Defacing the Humble Stone is an unmarked quest in Fallout: New Vegas.

Detailed Walkthrough
When visiting the War Memorial at Boulder City, you will meet an NCR soldier, Private Kowalski. He is paying respects to his brother, who died during the First Battle of Hoover Dam. Keep being disrespectful or apologize (Speech 30). Whether you have completed the quest or not, Kowalski will disappear after few days.
 * Aim at the Memorial and Kowalski will become angry, shooting at it will make him furious.
 * If the Courier insults him and his brother, the Courier receives negative Karma and makes Kowalski hostile (killing him this way doesn't make other people hostile).
 * If the Courier doesn't apologize, he receives NCR infamy. If he shoots at the memorial, this makes all people hostile, including Kowalski.