Oh dear god. First of all, I'm sorry I didn't reply to this when I really should've.

Beast... really really doesn't like Isaac right now. If anyone asked, it's likely he would say he even outright hates the guy. At first, he tried to not judge for Belle's sake, when he allowed Isaac a room in their house that one night, but his lack of gratitude already guarded him off, and his treatment toward Belle just before Christmas shot the scale of caution all the way up to extreme discontent. If he could have it his way, Isaac would stay the hell away from him, and especially the hell away from Belle.