I get what you're saying, but you're wrong.
The problem here is that they aren't catering to the Tumblr social justice/SRS/LGBTQ community with their pornography. You'd find that people who are into those things are heavily critical of porn as a whole (I can provide some anecdotal evidence, if you'd like, but I'm hoping you appreciate and accept that) and are unlikely to join the website anyway. Being classy and artsy doesn't mean that they have to avoid potentially offending people: in any case, is anyone
actually offended by the name Tranny Art? Have you spoken to any members of the trans community that are outright against this? I'm sure you could find cases where they're against the word as a whole, but those arguments are questionable given what we know about language.
See, language is used to convey an idea. The whole purpose of words is to get what's going on in my head into your head. That's it. When I use words, I use them to transfer whatever it is going on in my brain so that you get what I think, believe and feel. Now, no matter what language I use, if I'm conveying the idea to you, you should focus on the content of that idea
in and of itself, with little regard for what I used in order to put it there.
Using the name "Tranny Art" means very little, but when we combine it with the content of the site, the attitude of the people involved and the way that's it being marketed, perhaps we should see that the word isn't supposed to be offensive or damaging. It's just supposed to convey the idea of what's going on behind the scenes. Generally, people into porn are happy to use the phrase "tranny", they don't do so negatively or with hate, they just do so because it accurately represents what they want.
Let's take an example of the way that words can/cannot be offensive in given scenarios.
1. I have a friend who's the biggest fag, but I absolutely love him to pieces. He's one of the most adorable people you'll ever meet.
2. I think that populations that were native to the land known as 'Australia' should be gradually reduced by the government to better improve the country.
Now the former uses the word 'fag', a word that you'd probably consider to be offensive, correct?
The latter uses absolutely no words that are individually classified as being offensive. There's nothing there that would, on its own, signal someone to think that it contains a negative message. Yet when we compare the ideas conveyed by both of the concepts, the former is a message of love and the latter is suggesting mass killings of a certain race. What am I getting at here?
You now accept from my second statement that it's possible for someone to say something racist/hateful/disgusting without using allegedly racist/hateful/disgusting language, so what's the problem with believing that it's possible for someone to be doing the inverse? That is, using allegedly 'bad' language to convey an idea that isn't 'bad'.
Now - I don't know if this company considered what I'm arguing here, and was happy to use the word for this purpose, but if you're going to insist that people think critically, I'd urge you to give a reasonable, logical and falsifiable argument against what I have just concluded.
To make that extra clear, here's the bottom line and tl;dr:
Individuals should not question whether individual words are offensive or not. They should instead consider the context and purpose of individual words to critically assess whether the idea behind the usage of that word is one that is negative, hateful or offensive.