To have experienced inferiority as a direct result of the actions of another party. For the expression "shat on" to make sense, there must be a recipient (the one who is "shat on") as well as a perpetrating party (the one who "shat on" the recipient). The perpetrator's actions or remarks can be bold, such as the actual physically shitting on the the recipient, or subtle, such as saying something to someone else that implies that the recipient is in someway whack or lacking a ballsac. However, the key takeaway from use of this expression is the fact that the perpetrator's actions, though they can be cleaned up (just as shit can be cleaned off of a toilet) are essentially irreversible, since the smell--not to mention the memory--of shit is virtually impossible to remove once it is dropped upon a target.
The charmingly aggressive, and yet so unfortunately cunning, young men virtually shat on their neighboring organization's lawn of dignity by taking home the gold that night.