There is a fine line between sticking up for yourself and enhancing your promotional opportunities or long term employment.
Proving you have been discriminatated against is rather difficult if the reasons given for your lack of promotion appear to an outsider to be reasonable even though you and everyone else knows the real reason.
Who these days would publicly state the reasons for lack of promotion being on the basis of gender, race, sexuality, someone who sticks up for themselves or others etc? I think they are the reasons in many cases but these are not the officially stated reasons so it is only the idiots who get caught out and you probably wouldn't want to work for them anyway.