One of the main reasons that we encourage players to post their chat logs here is that us here on the Boards have an unbiased view of the situation. We see only your logs, with your word about what may or may not have happened in the game (if there was a 4v5, bad baron call, team getting aced, etc...) The downside to that for many posters, is that they tend to think "well, you'll never know what those guys were saying to me. It was awful!" That is true. We have no way of knowing what was happening with the other player's chat, but to be honest, we don't need it. Our only concern is helping you.
We go through the logs, without the irritation and anger that you, the player, feel, and look at them with fresh eyes. We run them against the sorts of things that we see in our own matches, and the things that we see in the chat logs of other punished players. After doing this a while, most of us can give you a pretty good idea what caused your punishment, or, can point you in the right direction if it appears to be made in error. It is possible that it was done in error, and in those cases, it can be lessened or even completely removed, depending on the error.
But that first step always comes with us seeing the full chat logs.