As a trans woman I don't tend to consider this word to stand for anything meaningful.
It has been so overused in trivial situations that it has lost all value even in cases where it might be true.
That's what happens when you over react to relatively minor things.
Like the trans boy who cried wolf when a mouse walked by, so that when the wolf does come to get you people shrug and say - not you again.
I would just suggest asking yourself, if someone said that to me about me then how would I react?
If you just would feel puzzled or mildly aggrieved but that mistakes and misunderstandings or different views on things can happen.
Then it is not transphobia so move on.
There is way too much over reacting around this word and it is entirely counter productive.
It only makes those who might agree that some comments are unreasonable eventually think otherwise.
They might decide - well, if we have to watch every little thing we say or we too will be guilty of this without intent - then perhaps the one I thought was transphobic when I saw it from someone else yesterday really wasn't.
Just stop calling everything transphobia.
Much of it is no more than a different opinion from the one you hold.
If it hurts then look to yourself and ask why. You have no right to presume everybody believes everything you say or supports everything you do.
After all, by telling this person they are wrong right now that is pretty much what you are doing to them.
In the English language we call that honest disagreement.
And most of the time it would really help trans people to accept that, shrug and get on with their day.