I think this is pretty self explanatory. Only one person complaining vs 50 people complaining? Do you realize how many people have an Xbox live account? I wish I had a legit number for you, but I can tell you it's a VERY high number. They can't be everywhere at once. They will get around to checking into it, more often than not thou "the complaint" can't be proven. You do realize you can block people right? So you'll never appear in a game with them again. Try this instead of reporting them.
I see quite a few complaints about Xbox live, from most it seems as though the automatic reporting features in the game tend to be broken. Xbox live is more of a popularity contest where large groups and communities have the power to hurt others based on collusion and banding together.