I don't know what inordinate advantage you are supposed to be gaining by being able to do a little extra damage with a thrown rock.
You're right, of course, but being right doesn't always help when you've got a drama queen/control freak/overly sensitive DM.
What might help is this: Pick your battles.
Is it absolutely vital to you that your table adhere to the RAW?
Or can you let the DM have her little despotic leadership for now?
Maybe you can take over DMing in a few months, if you'd like.
My usual situation where a DM is wrong (intentionally or not) about the rules is to say, "Hey, the rules say X, if you want to do it by them, but if not, it's your game, dude." Sometimes the DM will be totally fine with RAW, sometimes they'll prefer what they have in their heads, but in both cases, it IS the DM's choice.
No message board consensus or rulebook is really going to functionally change that.
You are right. Be proud of that!

But unless it's
really important that you be right on this, just drop it.
And maybe next time the DM is wrong, don't bother quoting RAW.
I would advise you to try and take the DMing helm later on, if you can. Often, one of the best ways to gently show DMs things like "Adding DEX mod to a thrown rock won't break your game!" is to demonstrate that it is possible yourself. That's not always possible, but it wouldn't hurt to ask. Not now, of course. Wait a few weeks.
It seems like your DM got a little testy about...something. Maybe it doesn't have anything to do with the game. Maybe the way you phrased your response he took as rude. Maybe he's just generally tetchy about D&D. Whatever the case, friendship > RAW, so shrug, maybe with a "Dude, I just thought you might like to know the actual rules, but whatever," and keep on.
Unless it's a Really Big Deal to you.
In which case, chill out, and THEN do the above. Or just ditch the group.
