What is sexism? I am sure that there are many definitions, some of which people do not really want to admit to, but the one to be used here is: using gender as a differentiating factor. Really, can there be any other definition?
Let us consider some examples.
The new Ghostbusters movie has women as the primary characters. It is unfunny. Is this sexist? No, it is just unfunny.
If I address a man as sir, is this sexist? Why, yes it is.
Men are sexually attracted to women and not so much to guys. Is this sexist? Yes, it is.
Men and women have different plumbing? Yes, this is sexist.
Men and women have predispositions to think/feel differently? Definitely sexist.
Women favoring laws that help women at the expense of men, i.e. the feminine imperative. Most truly sexist
A woman owned company that will only hire women, and is proud about it (I know of several such outfits). Clearly sexist
Your job is to state whether sexism is good or bad. Furthermore, you can refine the definition as to how it truly is interpreted.