when i took abnormal psych, my teacher explained that these types of thoughts are normal to an extent. he used the example that his wife was getting something out of the fridge and she saw the butcher knife sitting there on the counter and he had the fleeting thought to pick it up and stab her in the back with it. he says every body experiences these types of thoughts at one time or another and they are completely normal, like driving into oncoming traffic or jumping off a bridge. i dont know if this applies to what you are talking about or not.