I don't "hate" it.... I just think it was ill-advised to make this sort of "thou MUST" imperative part of a faction questline. I don't myself play weres or vamps - sorry, just NOT my thing, never has been never will be. So finding out early on my first toon that in order to actually complete one of the major faction questlines required me to go somewhere not ever in my choosing (no, I don't care that it can be "cured" later, that's not the point) was a huge letdown.
I understand that because I think that was a really poor decision on Bethesda's part, but because I like werewolves I thought it was cool. But agin I completely get where you are coming from.
I think it isn't really known the the Silver Hand are werewolf hunters. They seem to be bandits first and foremost, who also target werewolves on the side. They attack and kill people who have nothing to do with the Companions and have the basic dialogue bandits do (paying off bounties, wishing they could turn wood into gold, etc).
The Companions most likely were hired to attack the Silver Hand at some point, and during this the members of the Circle on that mission were forced to transform. They killed the bandit leaders but someone probably survived who learned their secret and the group decided to target werewolves as a way of getting back at the Companions. They most likely kill other werewolves as a form of practice and to study the werewolves so they can prepare for their attacks against the Companions.
That makes the most sense because I get the feeling that the Silver Hand just have a personal vendetta against the Companions more than anything.