Why should I know what is evil?

عرفت الشر لا للشر لكن لتوقيه *** ومن لا يعرف الشر من الخيريقع فيه
 
I acquainted myself with evil not for  the sake of evil rather to avoid it.
And who ever does not recognize evil from good, will fall into it.
 
Allah protect us. ameen