I agree with you, but I don’t agree with the way you are presenting the point, and it could be a miscommunication, so I’ll explain:

Historically, ‘All Lives Matter’ was used to diminish the BLM movement. It is used as a response when it should be the premise. All Lives Matter, therefore Black Lives Matter, not the other way around.

I think the comment replying to you was using the All Lives Matter metaphor to say that your comment about it being a human being that was killed is deliberately ignoring the struggles for trans people. But the way they phrased it was very subtle.