it wasn't once. It's happened more than once, and people have corrected you more than once. Not only that, when your apologies are as hallow as the one you gave, it's pretty clear that you don't really give a shit about what you did. Don't claim to be our Ally when really you don't care at all.
I'm not mad, I just want you to do a bit better. Like if you don't know something, research it or something like that. And what you need to understand is that a lot of people, especially in regards to gender, have faced a lot of discrimination and hurtful/ignorant comments. People can get overly defensive because of that.