Am I considered transphobic and how bc I’m genuinely confused.

I was in an argument bc someone vented that they wanted to rip out their moms skull and hope they die in a gruesome car accident of which I said “I understand you are frustrated but isn’t that a bit too far?” Now for context their mom will make them apply some make up every once and a while for events etc. and what set them off was their mom took their makeshift binder. Immediately everyone started calling me transphobic when I even specified it was what they said not why to which they all replied “you aren’t trans you wouldn’t understand.” Of which is true but I fail to see the relativity. If I am in the wrong please tell me how and how I can do better.