Tamara, this seems to me like a bit of a logical stretch. Now, I don't know the exact intention of the author with this line, "Marsha P. Johnson, Sylvia Rivera, and a slew of other gay men of color", but there are are least a few ways of looking at this:
1. From a grammatical viewpoint, note the Oxford comma after "Rivera" which makes for three distinct elements that stand alone.
2. From a context perspective, the author is talking about his experience as a person of colour and as a gay man. Again, I don't know his personal views, but I don't think his intention was to invalidate trans lives.
3. From a clarity perspective: yes, this sentence could come across as problematic, but is that the truth? Does the context of the piece lead you to believe that it is the author's intention is to invalidate trans lives?