Although you lectured me on terminology I am likely more understanding than you are (and I chose my terminology for specific reasons).
Out of curiosity, what are these reasons? I think most transgender people find it hurtful when you use pronouns that label them by a gender other than what they've chosen for themselves.
Saying that you're "likely more understanding" than Samith and that you used this terminology intentionally seems an awful lot like you're saying "I do understand how hurtful calling a male-to-female transgender person 'he' can be, and that's why I'm doing it" although I think/hope that that's not what you actually mean.
EDIT: Having read your post again it's very clear that you were not willingly causing offense, and you're by no means in the wrong based on the fact that this knowledge changed your feelings toward this person. I just thought your choice of terminology was odd especially coming from someone who understands these issues, and it does seem possible to construe what you're saying as deliberately hurtful even though you don't mean it that way.