Catelyn Stark is one of the few voices of reason in A Song of Ice and Fire, but she is repeatedly ignored, because she is a mother, and because she is a woman. Although, like every other character in the series, she is fallible (trusting Littlefinger, for example), her advice is generally sound. She has lived through one bloody war and lost people she cared about as a result. She does not want to live through another one and lose all her family. And so she alone, out of all the main characters, speaks out against war and vengeance. She understands that further death and destruction will not bring back the people they have lost. More than anything, she wants peace. She warns Renly that his men are the “knights of summer,” playing at war with no understanding of its reality. She combines experience with wisdom, and many of the terrible situations in the books could have been avoided if people listened to warnings.
But they don’t. Because she is a woman, and because she is a mother. Because, as a mother, she is dismissed as too soft-hearted, too concerned with protecting her children to understand the true nature of war. Because, as Robb‘s mother, heeding her words would be seen as weakness.