It's kind of funny... in a weird way. I personally don't think what you said was rude and could see myself saying the same thing easily without thinking anything of it. BUT, I can also easily see it causing big issues.
It's a lot different reading something like this and responding, than it is to actually be involved in the situation on the receiving end.
My son does this a lot to me. I have to decipher whether or not he's intentionally saying things to me purposefully or not, and that is hard to do as well as an autie. Because, believe it or not, lol, he DOES do it on purpose at times as well... and that makes it very hard to figure out how to react.
Now, if he says something like "I was just saying..." then I know he likely didn't mean it to be rude. When he fixates on it, that is my queue, pretty much.
I've explained this to him... that I mess up ALL THE TIME when talking to others, lol, but that means I know what it's like too, so he needs to tell me if he meant it or not. It's hard not to take a lot of what he says personally, because he has meant it to be that way in the past many times.
For instance, I told him to do something one day, and he said "I don't have to listen to you, you know". What? Did he really just say that??? He laughed at me after saying it. Then, he realized he was making me angry, and covered it up quickly with, "I mean, technically, I could make my own choices, but would probably get into trouble a lot... so what was it you wanted me to do again?"
When things like that go on a lot, it's really hard to interpret the initial statements as anything but smart aleck. Does that make sense?
I have a feeling, that your stepdad was probably thinking you were intending it to be that way, and if he thought you were intending it that way, his next thought was probably, "why won't she do it herself?".
It's really tricky stuff... my mom used to get mad at me all the time for things like that when I didn't mean anything by it. Now that I don't live with her, she realizes I'm not meaning things that way... but I think it made a big difference while living with her, because she was in full parent mode, in which case, sometimes you just expect your kids to be that way and don't see the difference.
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Sorry about the incredibly long post...
"I enjoyed the meetings, too. It was like having friends." -Luna Lovegood