Hey Ed,
I sympathize entirely, and I'm sorry that this happened to you. Just a couple of thoughts:
1) As much as I might like to live in a world devoid of verbal abuse, racism, etc., such is not the case, and I tend towards the idea that freedom of expression must include the right to express attitudes and ideas that are repugnent to me.
I just don't hang there. Different forums set different standards, and fortunately, the web is a big enough place for all manner of ground-rules to coexist.
I probably would have put the people who made fun of your impairment into the "pay no mind" file and not responded. But of course that's easy for me to say. If it were me being attacked, I'd probably want to stand up for what's right, too.
One time about a year ago I stumbled upon a "music" forum where a whole crowd (including the moderator) were absolutely UNLOADING on some poor guy who had expressed an unpopular opinion. I humbly stood up for him, (I hate seeing people being ganged-up on by bullies) politely suggesting that their crude, obscene remarks demonstrated a lack of class, and so they started pounding on me, too. Since life is short, I just split.
BTW, besides SZ, Northern Sounds Garritan (GPO) groups are extremely positive, and people are encouraged to participate regardless of their tech or musical abilities. The idea is to foster a nurturing learning/teaching environment where no one need feel inferior or embarassed. The scenario you just described most certainly wouldn't be tolerated there, and there are NI discussion topics there as well:
http://www.northernsounds.com/forum/index.php? The good news is that most people are decent, it's just that the few bad apples will invariably pop up from time to time. I'm afraid there's no getting away from that.
Cheers,
Michael