It's not that they turn "crazy," it's just that they seem like it to those that it imprints on, like humans. What it instinctually knows as normal bovine behaviour, is "crazy" or "bad" in human behaviour terms. A calf--any calf really, but the emphasis is on bull calves--can grow up to be dangerous if not treated like a bovine and taught how to be respectful and submissive in bovine language. Dangerous grown-up bottle-babies come about when they're treated like pets or like a four-legged human and when a dominant behaviour is seen as "cute" and allowed to continue up until they are seen as bigger and more scarier to it's human herd. People have been killed by bulls that have been bottle-raised like pets and have grown up without the influences of others of its kind early in life and have not been treated like a bovine or rather, treated like a full grown cow or bull.