"Not that feminist crap again!" - one of my favourite comments on reddit/youtube/twitter/all-the-social-media.
Perhaps the reason why so many people feel uncomfortable with the word "feminism" (apart from the obvious popculture bastardization of it), is the emotionally charged nature of the topic. Just like any other oppression theory, it is hard not to get anecdotal when supporting or opposing it.
I'll try it anyway.
--- "Kitty, why are you a feminist?" ---
Well, stranger, I'm a feminist for two reasons: one is based on political philosophy and one on moral reasoning.
Politically, I adhere to the theory of justice after John Rawls. Simply put, Rawls thinks everyone must have equal rights to basic liberties (like i.e. the ability to vote and the ability to walk free if not a proven criminal) and that those most-disadvantaged need to be supported in a way that they have the best opportunities to have access to their right to basic liberties.
Basically, he wants things to be 'fair'.
Consequently, by subscribing to this view, I must be a feminist simply by default of what feminism is: the wish to equalize a disadvantaged group to give them access to basic liberties.
Morally, I am against oppression. If you too are against oppression, then you must be a feminist by default again. Sexism (and misogyny) is a form of oppression. Feminism is a theory that seeks to obliterate sexism. Thus, feminism is a tool against oppression.
It is not possibly to completely eliminate oppression as a whole without eradicating all forms of oppression. If one form of oppression persists, eradicating another will not be fully possible.
Thus, politically and morally, I'm a feminist because I have to be.