Trans people in support groups accept one another as male and female because they can relate from their own experiences. People who cannot relate cannot "accept". Someone who has never had the experience of being trans can't appreciate what a trans person can, cannot accept what a trans person can (in my experience of roughly 12 years since I started this process this has been my experience.
You have to explain what you mean by 'accept', you have to define the word or rather the words you are using. If 'acceptance' means someone is okay with you or okay with your transition then that is 'acceptance'. 'Experiencing' you as female is different from accepting you as a trans woman. Being okay with your transition, being okay with your wearing female clothing, being okay with how you act or talk or dress yourself is 'acceptance' but 'experiencing' you as female is not the same thing.
Accepting you into the group is 'acceptance', it does not equal 'experiencing' you as female. "Accepting you as one of the girls is acceptance but experiencing you as female is not a conscious choice. Human beings cannot make a conscious choice on how to experience you. They either know you on a subconscious level of female based on gender cues or they know you based upon conflicting information.
If you watch a YouTube video of a UFO and then someone shows you evidence that it was faked you can't experience that video the same way ever again, no matter how much you choose to "accept" it you won't look at it the same way, you can't. It isn't a conscious choice you can make. Instead when you find out the video was faked when you see it again you will pick out details that confirm for you it was faked.
When trans women find out some other woman transitioned they are able to 'accept' her because they know what it is to be trans, they know what it is to be female even when one's body is male. Trans women can therefore view transition as a way of manifesting what is already there, as a way of overcoming a disability or revealing the truth, non-trans people experience it altogether differently! Non-trans people cannot relate from an experience they have never had, the experience of being female even when one's body is male so to them when they find out a woman transitioned they garner an entirely different "truth" and how they experience that trans woman is permanently changed. Non-trans people experience male body as male mind, female body as female mind. You can tell them there is a world where up is down but it won't make any practical sense to them and it won't allow them to experience being another gender.
Transsexualism was once referred to as a conundrum. A conundrum is something that cannot be understood, a riddle. Because in order to understand it you have to experience it for yourself. Otherwise male is body and mind, female is body and mind and there is no separation of the body and mind because no one else (the majority of people) have never experienced life that way and it is inconceivable to them. Most people don't want to bother with something they cannot grasp (especially when there is no reward in it for them), they have their own lives to live so they will casually 'accept' you. But how they 'experience' you is not a conscious choice they are even remotely capable of making. And think about it, lots of people experience GD (gender dysphoria) but how many of those people are willing to make the effort to change their lives and yet we expect others to change how they relate to us? Education and continuing education allow people to accept us as trans, how they experience us can never be an issue of 'education' rather it is an unconscious choice based either upon subconsciously recognized gender cues or conflicting information.
Trans women can accept another woman when it is revealed that she is trans because their truth is that she has always been female and this is the conundrum, non-trans people cannot accept that she has always been female because they 'know' she was male and that changes how non-trans people see her. Sure non-trans people can choose to "accept" her but how they will 'experience' her is not a conscious choice they are even remotely capable of making.
Could someone be so intoxicatingly female that the gender cues she gives off could over-ride any conflicting information that people have heard about her? This isn't an all-black or all-white world, different people experience things differently and have different motivations. My parents accept me as female but they don't experience me as female. They are kind - out of their love for me and have made changes to incorporate me into their lives, pronouns and such... Lots of people are willing to do that because we tend to live in a polite Society or at least one where most people want to avoid offense. I was in a very sexual relationship with a guy who was super into me and he probably knows I transitioned. He never said anything about knowing I transitioned probably because he didn't want to loose me. But it got too creepy for me because we have mutual friends and really he wasn't a good guy anyway. And my mutual friends talk, lord do they talk, there was no way he hadn't heard about me but did that stop him from having sex with me, no.
Would he have been happy to stay in a relationship with me for the rest of my life? Yes. Very much so. And I think his penis accepted me as female but his mind probably had some conflicting chatter in it. If his sexuality had ever been questioned because of his relationship with me he would have had to ask himself questions that other men will never be posed with.