There is no evidence that werewolves hate crosses. Werewolves are fictional creatures, and their traits are determined entirely by the author or creator who imagines them.
The association between werewolves and crosses likely stems from the broader folklore linking vampires and crosses. In traditional vampire lore, crosses are depicted as symbols of protection against vampires, who are said to be repelled by them. Since werewolves and vampires are both associated with horror and the supernatural, the connection may have been influenced by vampire mythology.