What's total BS is saying that genital preference is transphobic- it's not.
Most of the article is bullshit. I don't want to have anything to do with penises, they freak me out- which is my personal sexual preference, and has nothing to do with anyone else in specific.
Where they do admittedly make a point is that in turning down sex or a date or what have you- you don't need to give a reason, and if the reason is genitalia you probably should keep it to yourself.
It's a valid reason- but if you're aware it's a sensitive spot for a person you can exercise judgement and not give a reason.
But to say that a genital preference is transphobic is nonsense.
But honestly the likelihood of this kind of thing coming up is so slim, IRL trans people I've met aren't like this at all, the tumblr crowd as a whole can get... intense.