So you are upset that a group is focusing on helping trans-people gain rights instead of focusing on same-sex marriage, even though you have admitted that there are plenty of other organization already focusing on that? YABU yes.
As a queer woman, I am glad some associations/organizations offer support targeted at trans people, LGB people tend to have had groups focused on them for decades so I do think it's only fair and considering plenty of organization are (according to you) working towards making same-sex mariage legal in that country, I can't see how this one organization focusing on trans people could in anyway damage the issue of same-sex marriage in the country you are currently in (issue which will also affect trans people who have had their gender legally changed and are dating someone of the same sex btw).
I currently live in the US, where Trans people might have their rights completly erased and I have plenty of trans friends and I am glad some association are having their back and looking out for their interests (not saying this specific organization is doing it for the right reasons), trans people have different experiences and needs to the ones of LGB people (and even within the LGB community gay women and gay men also happen to have different needs/experiences), I mean you just have to look at mumsnet to see how accepting most people are nowadays of homosexuality vs how people react to any thing related to trans people (to the point that even just the word trans seems triggering these days!).
So no personally, I don't think one organization chosing to mostly focus on trans right is homophobic, the same way I don't think an association who focuses mostly on a gay rights is transphobic/trans-exclusive. I personally find it a bit saddening that you seem to want to divide our community when I feel we should all be looking for each other's interest/fight for each other's rights.
Also trans people can't really be held responsible for the decision made by a (cis) straight man to have his organization focus on them despite your wish to somehow blame it on the "trans agenda".
Yes, it does seem like the guy is wanting to look good and edgy being a vocal LGBTQ+ activist, but if it does help get more visibility and more rights, I can't personally be bothered to care. Most big brands who promote LGBTQ+ related items around pride time aren't really doing it for our benefits either, we still enjoy the fact that they do bother to do something though.