How do you figure? It doesn't require you to be anti-lesbian, anti-gay, anti-bisexual, or anti-trans, in order to question why we lump together people who are homosexual/bisexual (which describes the types of people someone wants to get into a romantic or sexual relationship with), with people who are trans (people whose assigned-at-birth gender is not who they are).

The answer is, of course, that "we" don't lump them together; the group as a whole has decided to band together because the persecution and opression they suffer is in many ways shared, and often the kind of person who would persecute one of the groups would persecute all of them. But it's not "anti-trans" or "anti-LGBT" to ask this question.

(Consider "Asian-American", which is more a political/activist construct than anything else, given that "Asian" describes a bunch of different groups, some of which may not have all that much in common culturally or even politically.)

The organization in question may also be anti-trans (or anti-LGBT as a whole), but that's... a separate issue?