http://revach.net/article.php?id=2126

Section: Moadim   Category: Pesach
A Vegetarian Pesach in Kotzk?
Someone once asked the Kotzker Rebbe, if the Torah is so machmir on even one drop of Chometz why eat matza at all.  One mistake in the bakery and you can end up eating Chometz.  Why not just eat vegetables for the entire Pesach and staying as far away from Chometz altogether.  Similarly the Shir Maon asks, why do we make matza only out of a kind of grain that could become Chometz.  Let’s eat matza from rice, which has no possibility of becoming Chometz.

They answer is that our avodah is to vanquish the Yetzer Hara.  Battling him and winning is our purpose in life.  A person is not created like a Malach without a Yetzer Hara.  The yetzer hara is called Chometz (Si’or SheB’isah) as he spoils our purity.  We cannot avoid him.  We need to live with his constant threats but we are responsible to still keep ourselves one hundred percent kosher without a drop of Chometz.