I agree whole hardily with what my SO said. Mister, your comment was not only wrong but rather ignorant! Most people who are not trans, do not understand how we feel, or rather anything about us until they talk to us and learn. In the most basic sense, society teaches us how to think and react to things we see. "If it has tits and a crotch, it's female." is generally the as you say "basic" understanding of things.
Should someone label their SO as "FTM" and still refer to that person as "she" is only natural for someone who is just starting this transition (and everyone knows the SO has to transition as well, albeit in a different way.) Since I've met Landon I've known him as his born gender up until he introduced my SO and I to these boards. Since then I have referred to him properly, as I have learned and wish others to refer to me as. The point however, is simply this: How can we expect others to support us, when we do not support them?
SO's need support just was we all do, sometimes even more than we do! Getting worked up over the misuse of an unfamiliar term, or even asking something that may seem ignorant to seasoned members of the TG community, is just a prejudice as many things that can and have been said about us by others. Landon's SO may be ignorant about what exactly our community is about, in the sense that she does not have any previous knowledge about us other than what society says (which is generally very little.) However, harsh words and rejections such as your own, are NOT the way to help or endear anyone to even want to gain knowledge in this area. It would be the same as an African American child meeting a white person for the very first time and asking "Why are you so pale?" only to get the reply, "because your a stupid <insert N-word here>".
I guess what I'm trying to say is, whoever is making comments as such to any SO, needs a swift kick in the ass. Suck up your damned "pride" and help people to understand us more! That is unless you want us to be continually labeled as various unsavory words and thoughts, which these courses of action will only reinforce. Understanding and tolerance is a two-way street, we cannot demand people respect and tolerate us, without first respecting and tolerating others.