Is it really necessary to use gender-neutral language?
It is very important to use non-sexist language, even if a person does not have any discriminative intentions at all. Everyone, consciously or not, tends to assign masculine gender to terms, such as "man", even when this word is used for "human beings". "Man", amongst other expressions or grammatical constructions, should be avoided.
Every language reflects the prejudices of the society in which it evolved, and it is a fact that our society has been a male-dominated society. Language is naturally changing along with society. Our present culture still has many traces of sexism, prejudice and patriarchal society, and so has the language we use. But if language is changed, it may influence mind-sets as a consequence. Some years ago, no one thought German words like "StundentInnen" would ever be accepted, but by now it is in common use and it does not look unusual or strange anymore.
A similar process took place in English with terms, such as "chairperson".
Language and meaning have always been changing and we are aware of that developement. When we come across the word "Nigger", reading Huckleberry Finn, we do not assume that Mark Twain was a racist, because we know about the use of the term in that period. For a long time, people were using the expression "Negro" not being aware that it could offend a black person (in fact many blacks used the terms themselves, including Martin Luther King). But people have agreed on not using such expressions any longer, because even if not intended, they could still hurt someone's feelings.
One cannot tell other people what they mean by what they say and, of course, sexually biased language is rarely used deliberately. But there is the common principle that meaning...