Everybody tends to only positively think of him/herself, and negatively of other(s). On one hand it is normal, because no one wants to hurt him/herself; everybody wants a secure life. Yet, he/she sometimes negatively thinks of other(s) because many reasons. For example, he/she wants other(s) is just like him/herself. He/she does not want other(s) appear(s) different from him/herself. Another reason is he/she wants to dominate other(s). On the other hand this kind of thinking is totally wrong, because no one is perfect; everybody has his/her strengths and weaknesses.
Living in a society needs everybody`s better understanding of oneself and other(s). Since every one of us has his/her own strengths and weaknesses, we need one another. A weak one obviously needs the strong one. Yet, the strong one certainly needs the weak one in any way. In this sense the strong one may not look down upon the weak one.