Punishing and enslaving the innocent is what started and embedded the Capitol-inflicted atrocities in the first place.The suggestion by Coin was immediately appalling to even the victors (at least most of them) who had been personally and profoundly victimized by the Games.

The suggestion of a Capitol-kids Hunger Games as a means of punishment-by-proxy was the nail that sealed Coin's coffin. When Katniss has concrete evidence that Coin was simply another Snow, she put an end to it. Which is precisely what needed to be done.

Katniss' "yes" vote was a ruse to enable her to assassinate Coin. This is why we see the paragraph in which she says she weighed her choice carefully, and would find out just how well Haymitch knew her when she announced her vote. Haymitch, too, knew that she could not vote "NO" and retain her own life (she was already too much of a threat to Coin's political power). Her *only* option to end the Hunger Games forever was to vote "yes" so that she could still be out on that platform and in a position to ostensibly assassinate Snow, but in reality assassinate Snow's replacement.

When she added "For Prim", we knew for sure. Prim lost her life trying to RESCUE Capitol children - she would not have approved of killing them. The "For Prim" was a message to Haymitch that the vote she cast had two meanings. Haymitch signaled that he understood her message when he himself did not vote "yes" - instead - he said "I'm with the Mockingjay" - meaning - he's with the true rebel leader who would never allow Coin to rise to power.

Had Katniss voted "no", she immediately becomes a threat to Coin. The rebels would follow the Mockingjay, in terms of electing new leadership, and Katniss would *not* support Coin. Coin knew she was (politically) dead in the water if that happened. Once Katniss has no value to her - or worse, is an actual threat to her power - Coin would have her killed.

In other words, Katniss wasn't voting "yes" to another Hunger Games. She was voting "yes" so she could have the opportunity to end them once and for all. It was, in my opinion, Katniss' finest hour.

~Dr. B.~