Angry Christians aren't so rare, certainly not "weird", and there's a middle-ground between love and misanthropy. Many power metal (and related) bands have Christian lyrics that are not at odds with the fantasty lyrics that dominate that style. For those that do preach, I only see it as hypocritical if they choose metal solely because they think it's a niche for preaching. If they believe what they say and play with convincing passion, I don't need to agree with the lyrics. Plenty of bands preach about peace and etc from a secular viewpoint as well, and no one complains of any contradiction there.
I don't listen to metal for really any of those reasons, btw. I listen to it primarily for its bombast, passion, and riffs, which is why Burzum is the antithesis of the music that spawned motherfucking Judas Priest.