When a horse is angry, his ears will be pinned flat against his neck. In the picture, he doesn't look upset at all. When horse's ears look like that, they're usually bored, tired, or grumpy. The lunging thing is more of an issue, and that's a lack of respect. That should be dealt with by a trainer because a horse with no respect is dangerous.
I think part of his attitude problem is the fact that people pick on him all the time. That general vibe probably makes him more prone to misbehave and be in a crabby mood. And if people spook him on purpose and stuff like that, I would be grouchy, too.
No wonder he's not nice.