Wraith - The way to go with those guys is the opposite of the Goa'uld. Loose the haunted-house theatrics. Make them ordinary. They just eat people, that's all (and can't eat anything else.) There's nothing "abnormal" about them, from their point of view. All species have things they can eat and other things they can't eat, and they must survive within those constraints.
It's not the Wraith's fault that the only thing they can eat can walk and talk and shoot P-90s. In fact, it's kind of a bitch. I'm sure they'd prefer to eat something that won't start shooting at them.
How would Shep & the gang have reacted if the Wraith politely introduced themselves and explained the situation? Sure, we eat people around here. Do you expect us to starve to death instead? You could try to stop us from collecting our food source by violence, but you're only perpetrating violence against us by doing that. Of course we'll fight back. It's not like we have a choice.
Then Shep & the gang would be forced to admit they're taking sides with the humans simply because they're their own species - is that really a "good" reason to take sides at all? What makes humans so much more valuable than any other sentient species in the galaxy?