It's not that serious, why is this such a big deal over pronouns? There are so many things in the world for you all to be upset about, and we're upset for someone calling you the wrong pronoun? It is the internet! You will always be misgendered and a long list of other things because we do not see you in-person when we speak.
I do suggest in the future, if you're unsure, just refer to everyone as they or them if you're unsure as that's a neutral term. If anyone gives you anymore problems about this nonsense let me know :)
Just leave it alone and move on!