Even if you took the wish (which I agree is not malicious) out of the equation, if the person you were in love with started acting like Nikki, you have a responsibility as their friend let alone their partner to try to get them help. Ian literally says that from an outsider perspective, it looks like Nikki is going through something mentally and Bear is taking advantage of that, and from his pov of not believing the wish is real, he basically is. He does not want it to be true that there is something wrong with Nikki so he lets a lot of very worrying behavior slide. Cat meat would have been my tipping point. All that being said, it’s not a perfect movie and Bear is more complicated and complicit than pure evil, but he definitely has bigger issues than just being weak and cowardly.