I feel like you are acting like I am arguing your points though we are on the same side. And I think you can't justify it but it isnt a reasonable hate. MY prime example would be Captain Ahab from Moby Dick. Just because the world is dangerous doesn't mean that most people would shrug it off as "if happens." And I never mention taking on all the members of what particularly harmed you. Like I said you can know who exactly wronged you and find them. And even if it is instinct you would have to recognize that "They are a danger" which is what makes the Silver Hand an evil faction. Since they are just pure racists in that they dont care if you are a feral wolf or not.
Stormcloaks are racist too, true, they don't always kill races they dislike, but they're extremely racist. Yet everyone thinks they're the good guys.
So are the Dawnguard too, they slaughter every single vampire they find and purposely hunt them down, yet they are considered the good guys.
There is no true evil or good in Skyrim, it's all up to you and your character. We don't even know anything about the Silver Hand, yet you just shrug them off as terrible and saying having them joinable would ruin the game. (Someone said that, maybe not you. Not sure) Anyway, they could have a huge backstory we don't know about. A reason for their hatred of werewolves and vampires, likely it'd be a better reason than the one the Dawnguard has. Yeah, RIGHT NOW it looks like the reasons and actions are the same. But we know the Dawnguard's for sure, there's not any canon lore I know of relating to the Silver Hand.
Also, even if you do consider them evil, remember, there's plenty of those who gladly play evil characters all the time.
The Dawnguard are praised for fascist genocide, yet the Silver Hand are insulted and hated when we know nothing of them. Yeah, they attack "anyone" who comes by, but you have to realize, they don't show up in your game until you become a werewolf (I don't think they do anyway), so obviously they would attack you. The Silver Hand could likely be much better than everyone thinks, the developers just didn't flesh them out enough, I'm hoping they do next Elder Scrolls game. I really like the Silver Hand, I think many of my characters would gladly join. (And others of mine would gladly slaughter them.)
On the topic, I also find myself sympathizing with many bandits. I mean, "some" of them did become bandits by choice, but others probably had no choice. They probably had no other way to support their family and needed to start stealing. Once they got caught, they broke free, then they had to hide in the wilderness as a bandit to stay free. Many times I'll hear bandits say "Just one more good haul, then I can pay off my fine..walk into the city a free man..." So bandits aren't always mindless marauders. (Granted some of them are.)