Oh love. That discomfort you feel? That feeling that they must be wrong, that they shouldn't say these things? That's cognitive dissonance. That's a part of you realising that stuff that seemed very simple and straightforward when someone told you about it doesn't actually stand up when you look at it closely.
And that's ok. No one is asking you to hate trans women or reject your friends or anything.
But you can't take someone born male, who grew as a human with all the strengths (and weaknesses) of a male body, and all the privileges (and challanges) that society gives to those born male, and none of the challanges (and privileges) society gives to those born female, and say "oh but something in this male person's mind makes them more like a woman than a man, makes them not only not a risk to fenale people but actually interchangeable with female people for all intents and purposes other than sports and childbirth, that despite having none of the formative experiences of women their life journey is still that of a women and not that of the man's life they in reality did live, and not only that these male-bodied people are actually women, but furthermore than no other male-bodied people will ever lie that they are the same as well". You just can't.
Female people still exist and have needs, challenges and risks that male people, even the nicest, sweetest trans women, do not.
And we have a right to our own name, our own voice, our own spaces, our own expereinces, our own history and our own identity.
Because when a person stands in front of you and says she is a woman, she's not a woman because the name woman decribes who she woke up as today, it's because she has lived the life of a female person, growing from a baby to a girl to a woman, living that life from birth to where she is today, to get there.