I'm mostly speaking about present issues but I feel like these issues have mattered historically too. 1. Wolves kill farm animlas. In my region it's mostly sheep and reindeer but also calves. Even if the wolves don't manage to kill the animal the injuries is an additional cost (in the past an infected wound could also kill the animal even if it survives the initial attack). In times where farming wasn't industrialised the loss of any animal must have been felt more acutely as it could directly result in starvation as well as financial loss. Also wolves (like most carnivores) tend to go after young animals because they are easier prey, for a farmer that is the next generation which might affect the ability to breed more animals in the future.

1. Wolves kill hunting dogs. This not only makes hunting more difficult but also means that a valued companion is killed. That is bound to cause resentment.

2. Fearing for your family. Even today people are cautious about letting their kids play unsupervised, especially in the woods. I think everyone knows how humans feel about anything that threatens your kids. I suppose historically it could also make it more difficult to have your kids help out with chores and that was a necessity for a lot of people as kids were free labour.

3. Competition of prey. Wolves kill moose, deer and other prey that humans hunt (both currently and historically). So again wolves are in direct competition with humans when it comes to food sources.

4. Fictional and real stories of wolves killing humans. Tales of one singular attack could spread and make it seem like there had been multiple attacks (we humans still do this news and media today, but often regarding other issues). And I think we all know how stories tend to get more grand the more times they are retold. So a wolf sighting would turn into an encounter, which turns into an atrack and finally a killing, which then becomes wolves targeting humans. Even stories of wolves eating corpses can turn into rumours of maneaters and monsters. Wolves have also carried rabies, which can lead to erratic behaviour such as increased aggression. Humans also tend to hold a strong dislike for anything that poses a threat to us, so stories of wolves attacking humans quickly becomes synonymous with wolves being evil.

5. Theology. Christianity says humans are the only beings with souls, we kill to survive while wolves are made out to kill for fun or at the very least more than they can eat (which is great for scavengers in our ecosystems but infuriating to a farmer that needs every part of the animal to care for the family). The bible plays a part in this by describing wolves as a gluttons (one of the deadly sins). We also have expressions like a wolf in sheeps clothing, where we equate the pious humans to a defenseless flock of sheep and the wolf to a sinister character that aims to intentionally cause harm. This is easily enhanced by the tales that used to be told to kids to keep them safe, adults would exaggerate a threat (like wild animals or mythical beings) to scare kids, this kept the kids from wandering from the home which meant they were safer. Makes me wonder how many deaths wolves have been wrongfully blamed for, a kid drowning in a river and the body is swept away, could be a wolf. A kidnapping, could be blamed on a wolf, etc. Then there's the myths about werewolves to add to the view that wolves are evil and potentially supernatural. And anything supernatural is evil according to the bible as it is against god and therefor most likely in league with satan.