
The situation is not as simple as the Galland family not liking werewolves. There are two major reasons the Gallands are hunting them down, the first is to make money. They aren’t Van Helsing, who is typically viewing the occupation of monster hunting as protection of the innocent, the Gallands hunt werewolves, kill them, and then sell the wolves various body parts to people who see werewolves as cures to different ailments (see chapter 1). They are the mafia and this is a main source of income (see the beginning of ch 4-5). The second reason, and the one I believe you are thinking about, is the head of the family’s obsession for revenge for the death of his son and daughter-in-law, Joshua’s parents (also in ch. 4-5). However I think this is either a convenient excuse the head is using or he is just actually insane. Because as we learned in ch. 12 that the wolves responsible for Joshua’s parents death are already dead. But no matter what I think Joshua’s grandfather (the head) has always hated werewolves, I think he proved this theory by murdering Kiefer’s wife and children (ch. 8).
I think the one who saved Josh Garland/Marlene during the fight with werewolves back then was the leader, Kieffer. That's why he meet Josh directly at chapter 8 when he could easily sent someone else. He and Josh wanted the war between Garland and werewolves to end, but Kieffer is still being cautious because things might go awry and cause a bloodshed.
And that bloodshed is about to happen. The idea of sending a picture of Josh as a hostage to Garland is a very bad idea. It could only make them launch an attack to save Josh. They should've shot a video message of him being happy among them and said that werewolves are not bad as the Garland persumed. Or they shouldn't send anything at all.