Theres a saying "The enemy of my enemy is my friend" the argonians would obviously see that they would be next in Ulfric's genocide and help the Dunmer, as you said a lot. Opinions and conjecture, thats pretty much all your arguments have been.
French revolution, the revolution in which Switzerland fought off the french and became an independent country, villages that would rebel against the Nazis, and I have plenty more examples of where common folk outmatched the soldiers who had swords and armor and no, tons of Dunmer families still farm, have you not seen the farms in riften? Plus there are still farms in Morrowind.
Genocide? What race has Ulfric wiped out exactly?
Okay. There are two or three Dunmer farms. I thought we were discussing Windhelm. As for Dunmer farmers invading from Morrowind, well Nords attacked Morrowind left and right. There's a reason that the Dunmer didn't strike back when they were at their fullest.
Firstly really long time ago, secondly if the Nords at Windhelm are slaughtering a whole race of people in their city that isn't Nord why would the Argonians side with them? That just doesn't make any sense what so ever.
Again it would seem Helseth fought for the majority of the Dunmer population why your bring that up however makes no sense, the Morrowind of old is no longer. That's hundreds of years ago.
Again, the Nords outnumber both the Argonians and Dunmer. So even if they bound together it'd be a quick battle and the Nords would have new leather boots and elf-ear necklaces (if they really were so racist.)
"It would seem."
I've screenshotted just about everything Ulfric says in game save for at the end of the Imperial quest line, but I'll get that in the next couple days. I'll link the pages that have his quotes. If you can find something racist, feel free to post it.
http://steamcommunity.com/id/Levowitz/screenshots/?p=3&filter=app_72850
http://steamcommunity.com/id/Levowitz/screenshots/?p=5&filter=app_72850