Trans

I’m comfortable being a woman with my lady parts. I also like to pretend. I told people I was male (transmasc, specifically) so that I could freely experience attraction to just men without having the “straight” label.

This is the part people will likely get upset about. I'm not pretending when I say I'm a woman. I am trans. Trans folks have been begging for people to respect their identity. It has nothing to do with sexuality, I did not transition in order to be seen as a lesbian woman or as a straight man. I did it to be seen as a woman. The other labels are added on after.

The way you've worded this, it seems like you've taken the trans masc identity and the trust that's been garnered around trans identities and abused it. Your feelings about this are valid, but I really feel you should approach this differently.

If you are feeling uncertain about your gender, then explore that and determine if you truly feel that way. Maybe you are trans masc? Maybe not? If you find yourself struggling with your gender but not rejecting your assigned gender at birth, maybe explore what it means to be genderfluid or nonbinary?

If you feel this is strictly a discomfort with your sexuality labels and perception of them, please find some other ways to convey it that does not involve abusing gender labels.

... presenting as a trans guy helped me feel better about myself

I identify as a woman who wants a penis. I think I’m moreso attracted to the idea of having male parts than actually seeing myself as a guy,

It kinda sounds like a bit of dysphoria honestly, unless you just said those things because of guilt. As far as I understand things, wanting to have genitals that typically match the opposite sex usually points to some form of body dysmorphia/euphoria even though you say your current body is fine.

Also, I don't know why the shame from people you're around. It sounds like you're still figuring yourself out and picking a label that is the closest to what you feel like is only something that you can know. Maybe it's not the most accurate but it's not entirely off base.

It sounds like you're at the very least kinda queer and non-heteronomative. Maybe non-binary but that's for you to figure out. Something under the Trans umbrella sounds right to me.

What about being straight or at least having that label is it you dislike?

I think people would be upset about dishonesty, particularly if you present yourself as a gay trans man, which most people will take to mean you don't see yourself as a woman, for example. If they learn you are actually OK with your assigned sex at birth and you were pretending to be a trans man, I could imagine they would be upset because you were dishonest.

First of all, gender expression and being trans is a vast field. While there are a bunch of labels one can use and that fit for many, this doesn't cover everybody and their experiences.

Second, there are many forms of dysphoria, not all have to do with being uncomfortable in your body.

With understanding this and only having your description from this post, there are signs of both of this (at least some I interpreted that way while reading). As far as my understanding of the demi label goes, one only feels like that gender in certain situations or at certain times. If that is "on the internet" for you, then it isn't far fetched. While you feel comfortable as a woman, you also said you'd desire male genitalia, which even without any pain from it is still dysphoria. If you want to be perceived as male sometimes or just online, that's a form of dysphoria too.

I'd recommend to you to do some soul-searching and introspection to find an answer for yourself. It doesn't sound like you're trans-masc, but maybe demiboy, genderfluid or non-binary would fit you? Nobody can answer that for you though and it is fine for you to be something that doesn't have a label.

Now I would say it's kind of inappropriate to call yourself trans-masc online if you don't consider yourself that. It might be seen as appropriating an identity or pain you don't actually have. Many trans people suffer from their dysphoria and taking that label just for the optics is maybe not that nice (similar to how people pretending to be another race isn't a good thing). Connecting this to my previous point: many trans people do start out pretending to be another gender online to experiment. If it feels comfortable to you, maybe you should think about that a bit

I think it kind of smacks as someone who wants to appropriate a struggle that is not their own.

I think most people have known a girl who claimed she was bisexual because she found some actress attractive and she wanted the attention from her friend group but found the idea of sex with women as disgusting and so never ever had a relationship with any women.

It wasn't too long ago that being gay or lesbian meant you had to hide who you were or who you loved and a lot of older people had to live through that. Some people still do to avoid losing their family. A lot of younger people don't understand that. So seeing someone who enjoys the privilege of being straight and being able to openly love who they want pretending to be marginalized just feels kind of gross. Kind of feels like Rachel Dolezal. You can look her up.

I'm probably going to be downvoted for this opinion but we were asked to explain why those around OP thought their deception was bad. This is likely why.

when ppl pretend to be a gender online because of comfort, it seems to me that they feel more comfortable as that gender

i would do some real reflection about this. you talk about gender dysphoria but you don't make any mention of gender euphoria. do you know what that is? it's the other set of traits to look for when considering if you're trans. one of those is feeling more comfortable in a given gender than your assigned gender at birth. another is feeling a sense of wholeness or happiness when picturing yourself with different sexual characteristics. sometimes that also presents as feeling sexually aroused when picturing yourself with those traits

why did you want to avoid being straight so badly?

i think online spaces are good places for exploring your gender identity and i don't really think it was wrong or disingenuous. you feel like it was, because it's pretend for you, but it's offering you a real sense of warmth and comfort, so i don't see an issue. obviously, please treat the trust that other people may grant you, given that label, with care. be a good person with it, and if they become close to you, consider explaining your situation to them, before misunderstandings can happen

identities are free to take and wear as you please. you don't owe anyone dysphoria or a desire to transition to be trans, or to be that identity everywhere at all times. it's just seems to me that you identify as a man/demiboy/etc online, and that's cool

who said it's bad?

I can see why people would be suspicious of you because this sounds similar to what a transphobe might do to mock trans men, but as long as you're doing this in good faith and not using it to overgeneralize anything I think it's fine.

It reads like you don't want to be a woman in a "woman" way? I think I get that. I'm transfem and gender fluid and sometimes feel like a man in a non-man way. But I generally don't tell people that because it might give them the wrong impression and make them treat me in ways I don't want.