Don't worry too much, most of it is just language issues.
Transmasculine: This word is really a misnomer, and some people find it really offensive actually. The problem with it is two-fold. First of all, it puts all so-called "transmasculine" people on the same spectrum. When most people use the word "transmasculine," they're referring to trans men, butch lesbians, female-assigned-at-birth genderqueer people... See a problem here? It's lumping people together, not by what they are or how they identify, but by the gender marker they were assigned at birth, and for many "transmasculine" people, that gender marker is wrong.
There's also the fact that masculine refers to a way of expressing oneself. It's the label you and other people apply to your actions. You can be a trans man and be more feminine than me; "masculine" wouldn't apply at all.
The dichotomy between "bisexuality" and "pansexuality" is similar. It's said over and over again that the word "bisexual" reinforces the gender binary, that if you're interested in genderqueer, genderfluid, agender (etc.) people, then the word doesn't apply, that you're "pansexual". (I've said this myself, honestly.) I've come to a point where I feel like a lot of that discourse is born out of both biphobia and transphobia. No one wants to be known as bi, cuz there's all that bullshit that bi people get from not just straight communities, but lesbian and gay ones as well. Also, in my experience, "pansexual" is largely used by people who just refuse to accept their trans partners identities. You see this a lot in lesbian communities; women who can't accept that they're partners are men, and they are, by definition, not in lesbian relationships with them.
There's another comment coming, sorry for rambling so much.
no subject
Transmasculine: This word is really a misnomer, and some people find it really offensive actually. The problem with it is two-fold. First of all, it puts all so-called "transmasculine" people on the same spectrum. When most people use the word "transmasculine," they're referring to trans men, butch lesbians, female-assigned-at-birth genderqueer people... See a problem here? It's lumping people together, not by what they are or how they identify, but by the gender marker they were assigned at birth, and for many "transmasculine" people, that gender marker is wrong.
There's also the fact that masculine refers to a way of expressing oneself. It's the label you and other people apply to your actions. You can be a trans man and be more feminine than me; "masculine" wouldn't apply at all.
The dichotomy between "bisexuality" and "pansexuality" is similar. It's said over and over again that the word "bisexual" reinforces the gender binary, that if you're interested in genderqueer, genderfluid, agender (etc.) people, then the word doesn't apply, that you're "pansexual". (I've said this myself, honestly.) I've come to a point where I feel like a lot of that discourse is born out of both biphobia and transphobia. No one wants to be known as bi, cuz there's all that bullshit that bi people get from not just straight communities, but lesbian and gay ones as well. Also, in my experience, "pansexual" is largely used by people who just refuse to accept their trans partners identities. You see this a lot in lesbian communities; women who can't accept that they're partners are men, and they are, by definition, not in lesbian relationships with them.
There's another comment coming, sorry for rambling so much.