Stereotypes typically involve taking what one sees as a general pattern in a demographic group- whether observed first hand or otherwise- and erroneously apply it to every member of said demographic group. All stereotypes are wrong- both logically and,in some cases, ethically. For example to say that men are stronger than women is a stereotype and thus wrong.
However, if one were to say that men are generally stronger than women, then that may be considered a proper generalisation and thus accurate and further more ethical. The nuances between a stereotype and a generalisation, produced by adding words or phrases that denote the pattern as general- in the case of a generalisation-, alters implications and connotations of the statement almost entirely as it takes into consideration the possibility of instances or variables that lie beyond what is the norm. Generalisations may also be considered more ethical as to articulate a stereotype when one is aware that it is not ubiquitously applicable can be considered as misconstruing the facts or one's observations.Also should the golden rule or the harm principle be given any weight in ethics, stereotypes may also be considered unethical; as you may be disparaging people of a demographic group and perhaps maybe in some cases hampering their individual development- as was hypothetically the case in a study when the stereotype that girls perform poorly in Mathematics generally negatively impacted some girls' performance in their Mathematics classes. It also is perhaps more coherent with " philosophical etiquette" as it takes into consideration that there may be known unknowns and unknown unknowns; I cannot recall the originator at this time but a philosopher one said that " It is precisely in knowing its limitations that philosophy exists"; in the scenario of the patterns we observe in people's characteristics we can take this a bit further and adjust the framework such that we may recognise where and to whom the pattern may apply and thus perhaps, in doing so, acquire a better understanding of ourselves and those around us.
At the same time there may be some positive benefits to negative stereotypes. Some people of a demographic may be hurt by the stereotype and thus seek to prove said stereotype- and its proponents- wrong by refraining from being able to be classed into the stereotype. Thus in doing so they may be free of the negative trait applied to their demographic. This, however, is not free of problems as such people may grow indignant with the stereotype and may develop low expectations of society or in personal relationships, perhaps going as far as to avoid many forms of closeness to others holding a "they will never understand me" paradigm.They may feel victimised.Although it should be noted that people may not fit into steroetypes regardless of if they are averse to them or not.
On a personal note, I generally view stereotypes as annoying and rather ignorant. And personally I believe that no label can ever truly describe who we are as individuals; for the most part I believe we make our choices as to who we are