There's so many problems here. Sadly, I'm a terrible writer and can't make a cohesive writing on what's wrong. Thankfully other people have pointed out all the problems!
I should add as an amendment if its not clear from the comic that trans men does not necessarily equal man with a vagina; as Bill points out, it's not a female body unless they label it that way, and different parts are labelled different things. I also think its a bit of a cop out saying 'I wouldn't put it that way but yeah basically' when you're asked about your trans partner's body. If someone said that about me (that I basically have a female body, when I've had extreme dysphoria over that) it would feel like a gigantic kick in the teeth.
If you're able to educate, leave it as 'I wouldn't describe their body that way: it's a male body.' Or simply leave it. Don't be a cop out and say something that could hurt your partner, even behind their back. And also, [some] trans men do have penises attached to them permanently, not just on the shelf. I see it joked around a lot that trans guys are better in bed because they have an array of d*cks, whereas many just own one for penetration and one flesh one which is attached to them. Some have a connection between the two: it's not a toy, it's their penis and you shouldnt treat it as an object. Or they could penetrate after an operation. I know lots of guys that like penetration penises to be as natural as possible- so not big purple and knobbly, but average sized and discreet. In all, I think this is effective for elaborating on my earlier post about genital attraction.
The reason why I generally don't date gay cis guys is because of this: they've been pretty much brainwashed by mainstream thinking that vagina is gross and they can't like it if they're gay. This is also the reason I've been with trans men only in long term relationships. And casual ->-bleeped-<-s. And basically everything. Amendment to the amendment: I'm often a lot camper than my male partners. Masculinity is redundant.
Also, that panel where he says he'd only be attracted to the same guy AFTER he's on T? I feel really weird about that. To me, that smacks of objectification; he's not attracted to the person, it's purely about the way their hormones make them look. If someone is ONLY attracted to me because I've got a certain set of hormones in my system at that moment in time, how meaningful is their attraction? This is a tricky subject, because yeah sexual orientation based on a "look" is a real and valid thing. I wouldn't expect anyone to be able to change what they're sexually attracted to, but I want it acknowledged that some preferences like this are almost undoubtedly based upon implicit cissexism. He uses language to disown responsibility for his attraction patterns by saying "my libido has its own criteria for when it responds." It's not him, it's just his libido.
It's unspoken that when he says he is attracted to trans* guys what he actually means is "I'm attracted to masculine, c*ck-identified trans* men who have been on and stayed on T at a full dosage for a while." That is NOT the same as being attracted to trans* men. This implicitly seems to assume that all trans* men are c*ck-identified, which they aren't. And that all trans* guys want to go on and stay on T, which they don't.
Plus, I (and many other guys) don't label that particular genital shape a "vagina" and it's gross having my body labeled that way without my consent by a cis person.
This whole comic sort of seems like "I'm open-minded because I'm less transphobic than some cis gay men, I'm so awesome because I deign to date trans* people. And poor me, I'm a cis person who has to field a tiny bit of transphobia, this is awful." Yeah, it's awful—now imagine how ->-bleeped-<-ed up this feels for his PARTNERS, at whom this transphobia is actually directed. Because let me tell you, it's sh*tty knowing that your partner's sexual orientation is questioned solely because they're with you. (Or, if you're dating someone who previously identified as lesbian, NOT having anyone question their sexuality just because they're with you) Not once in this whole comic does the author acknowledge that the flack he gets for dating trans* men is transphobia which might have a negative impact on his partners because it's actually directed at them, not him.
There's more hereOther people's words that were copy/pasted have been censored, and edited to be easier to read, but the linked post is not, and contains more content.