This is despite the fact that several countries have implemented similar reforms to their gender recognition laws without any negative impact to cis women whatsoever.
There is evidence, from every single country that adopted self-id in law and policies, that these have been used for purposes other than the intended.
Mexico: men undermine the democratic process seeking to grant equal representation to women by identifying as women;
US: rape, sexual assaults and harassment, intimidation, physical violence and aggression against women in prison (several law suits), in shelters and refuges for homeless and/or battered women, removal of fair competition in high scholl and college sport leading to the loss of opportunity and scholarships for girls; increase in voyerism and assault in sanitary facilities and changing rooms;
Spain: self-id abused by men tried for domestic violence offences to gain access to their children;
Ireland: a number of exemptions for privacy, now that self-id is being utilised by males who identify as trans and who have not fully (or at all) transitioned, issues are starting to arise;
Norway: self-id used by fully intact male to shower and undress in communal women-only changing area. When challenged by female user, management agrees this is not ok and communicates this to the male. Who does not care, does it again, is challenged again, then sues the woman challenging him for transphobia, discrimination and harassment. Three year journey through various courts results in judgement for the woman. In the judgement, the judge criticises the badly thought out law. Currently the Norwegian government is trying to push through an amendment to their hate crime laws that will make a fair, equitable and above all public discussion about how self-id harms women's rights all but impossible;
Canada: much discussed here, problems in prison, refuges, rape crisis support. Problems with women being sued for offering services specific to women for women only;
UK: self-id policies causing problems in all aspects of life that impact men and women, boys and girls differently.
There's many more examples from other countries, too.