It is fully false that only one male witness is considered as equal to two female witnesses for all cases. It is true only for one certain case. You will find only one verse in the glorious holy Quran/Koran, that says two female witnesses are equal to one male witness for one certain case. But all other verses in the glorious holy Quran/Koran that mention witnesses, without specifying male or female. There are 6 verses regarding witnesses. The specific verse regarding two female witnesses are equal to one male witness is Surah Baqarah, chapter 2 verse 282. This is the longest verse in the glorious holy Quran/Koran and deals with debt contracts. It says:
"O you who have believed, when you contract a debt for a specified term, write it down. And let a scribe write [it] between you in justice. Let no scribe refuse to write as Allah/(God) has taught him. So let him write and let the one who has the obligation dictate. And let him fear Allah/(God) , his Lord, and not leave anything out of it. But if the one who has the obligation is of limited understanding or weak or unable to dictate himself, then let his guardian dictate in justice. And bring to witness two witnesses from among your men. And if there are not two men [available], then a man and two women from those whom you accept as witnesses - so that if one of the women errs, then the other can remind her. And let not the witnesses refuse when they are called upon. And do not be [too] weary to write it, whether it is small or large, for its [specified] term. That is more just in the sight of Allah/(God) and stronger as evidence and more likely to prevent doubt between you, except when it is an immediate transaction which you conduct among yourselves. For [then] there is no blame upon you if you do not write it. And take witnesses when you conclude a contract. Let no scribe be harmed or any witness. For if you do so, indeed, it is [grave] disobedience in you. And fear Allah . And Allah/(God) teaches you. And Allah/(God) is Knowing of all things."
Above verse of the glorious holy Quran/Koran deals only with debt contract. For such cases, it is always recommended to make an contract in writing between the parties and take two witnesses, preferably both of two witness which should be men only. In case if anybody cannot find two men, then one man and two women would suffice. You have to understand that the social culture of that time and recent time were not similar. Country to country culture vary. In pregnancy some time women can not response at many events. In many culture women migrate to husband place after getting married.
For example, suppose one person wants to undergo an surgery for a particular ailment. To confirm the surgery, he would prefer taking references from two expert surgeons. In this example if he is unable to find two expert surgeons, his other option would be two general doctors who are plain MBBS and one expert surgeon.
Similarly in debt contract, two men are preferred. In a Islamic society men to be the breadwinners of their families. Since main financial responsibility is shouldered by men, they are expected to be well versed in debt contract as compared to women. As a other option, the witness can be two women and one man , so that if one of the women errs the other can remind her. The word used in the holy Quran/Koran is 'Tajil' which means 'to err' or 'confused'. Many have wrongly translated this word as 'to forget', but correct translation is 'to err' or 'confused'.
Other witnesses related verses of the glorious holy Quran/Koran are presented in following. While making a bequests or will of inheritance, two persons are necessary as witnesses. In Surah Maidah chapter 5 verse 106, the glorious holy Quran/Koran says:
"O you who believe! call to witness between you when death draws nigh to one of you, at the time of making the will, two just persons from among you, or two others from among others than you, if you are traveling in the land and the calamity of death befalls you; the two (witnesses) you should detain after the prayer; then if you doubt (them), they shall both swear by Allah, (saying): We will not take for it a price, though there be a relative, and we will not hide the testimony of Allah/(God) for then certainly we should be among the sinners."
"Thus when they fulfil their term appointed, either take them back on equitable terms or part with them on equitable terms; and take for witness two persons from among you, endued with justice, and establish the evidence (as) before Allah/(God). Such is the admonition given to him who believes in Allah/(God) and the Last Day. And for those who fear Allah/(God), He (ever) prepares a way out,"
Two persons endued with justice in case of talaq.
"And those who accuse chaste women and then do not produce four witnesses - lash them with eighty lashes and do not accept from them testimony ever after. And those are the defiantly disobedient,"
There are one particular verse of the glorious holy Quran/Koran from Surah Noor chapter 24, verse 6 clearly equates one female witness and one male witness:
"And those who accuse their wives [of adultery] and have no witnesses except themselves - then the witness of one of them [shall be] four testimonies [swearing] by Allah/(God) that indeed, he is of the truthful."
The seeming in Islam inequality of male and female witnesses in debt contract is not due to any inequality of the sexes. It is only due to the different natures and roles of men and women in society.
Here I attached some feminist women's video who were converted to Islam after a long research: