A little video

First, thank you EVERYONE so much for comments to my last post. You are all so sweet, and thank you for letting me vent away! All your advice was wonderful and I feel so lucky to have such great friends! I love you all!

Lately, I've been working on putting together a movie of all the little videos I take of Gage. So yesterday I decided to take this video to put on there, so I figured I would post it here!
Some of the words have Gage's own twist on them, and some of them we just taught him weird! :) Like he signs "milk" for "bottle" (because that's what we taught him) and when he says "I love you" he is trying to do the pinky finger, pointer finger, and thumb all up type of thing (confused yet?!). Anyways, I know it's long, but I hope you like it!

My disclaimer: No, Gage doesn't just sit by himself in his highchair like this! He just wouldn't stay focused on the ground cuz he wanted to play! So I am sitting right by him to make sure he doesn't fall! xoxo

Help... please...

Okay, I need help. Really bad. I have always been the type of person to avoid making someone feel bad, the type of person to just keep things to myself to avoid contention. But, as a mommy to a very special boy, I need to stop. Here's the situation...
Girl's night tonight. I went to have dinner and play Bunco with 11 other girls tonight (most of which I have only met once or twice before). Within the first 10 minutes I was there, someone said the "R" word (for those who may not know what word I am referring to, it is "retard") and another girl actually started a joke and laughing about it. Wanting to yell at them and run away, but wanting to cry at the same time, I bit my tongue and walked away to avoid the situation (THIS IS MY PROBLEM). Then later on in the night, I actually got into a small argument with a girl because of the way she was acting about having a child with Down syndrome, she made it seem like it would be the worst thing in the world, all while knowing all about my sweet boy. There was so much that offended me tonight, and I just didn't stand up for my boy like I wish I would have. I regret it so bad. I came home and cried to Derek and told him I don't know if I ever want to go back since it is something we do every month. I deal with this same situation at work quite often and then just get so angry at myself for not knowing how to approach the situation and stand up for Gage. I feel like a terrible mom right now for it, I honestly do.
So I am asking for advice. How do I approach this without creating a huge situation, but still getting the point across very clearly? I remember one time I did approach it and a girl actually started telling me why I shouldn't be offended by it because people don't mean it that way. Seriously? Don't tell me that I shouldn't be offended. I understand that people do it and don't mean it in a rude way to my little boy, but if I tell you that it DOES in fact bother me, don't try to defend yourself!
I don't usually do ranting posts like this, so thank you for bearing with me! Please help me, I feel terrible for what I did and I don't want it to happen again. Thank you for your advice in advance.