We have all had the boss that no one really likes, that comes into your room and scream at you. Whatever you do it's not good enough. Yes, we all have had that boss.
Revealing, many artists are that boss. If you are an artist you are the boss, sure it doesn't feel that way when you sit in the record label room or in other situations. Still, it's your music that is being promoted and the people that work on the promotion team are in fact, your employees.
Sure, you can look at it like you are a customer. Same here, we all have worked in a job when they had customers that are just ugly, ignorant and you just want to tell them to shut up, but since this is a business you can't just do that. We all had that job!
And yes, many artists are that boss or that customer. In my daily life as a manager, my job is to get the artist away from the decision makers to keep them from looking like the bad person. Most of the time, because they are acting just like the person we all hate. The risk is that they accidentally do that to someone really important.