You are right. I wouldn't recommend literally calling a person names or doing anything uncalled for - i was exaggerating, just trying to say if somebody else you don't want taking the session over tries to you need to let them know that since its your money things need to be done your way. But see it from my perspective for a second - i was in a session recently where the engineer suggested doing something, i said no i am not interested in trying that - to which he just started doing it anyway. I was too polite to get rude, but what are you supposed to do when somebody starts wasting 10 or 15 minutes doing something you told them not to do? When being polite doesn't get them to stop obviously more drastic measures need to be taken - as an engineer, you shouldn't put the client in a position of needing to raise their voice or something weird to get their point across. So it is also possible to be a nightmare engineer. Not listening, not doing what is asked, doing what they are asked not to do. Nobody wants to record with the nightmare engineer.
As far as the reverb comment, in theory you are right, but it can go the other way too. I have listened to people who said less reverb, no reverb, despite my want for it. Got the song finished, took it home, the band listened "it needs some reverb", so because i was too polite i wound up with a less than stellar result. Same thing happened with the Bass "more bass please" - "no, that won't sound good". Get the song home . . . can't hear the bass. If the engineer is going to deny the artist's request and force their decision it needs to actually work.
I have never been rude for a second to anybody in any studio - and i have always gotten pushed around and wound up with so-so results. The one engineer that got me the sound i wanted never questioned a preference i had, and decisions i let him make worked well and he didn't attempt to force ideas i wasn't fond of. I am a super polite and mild fellow in person, and i have allowed other people to hijack my session and i haven't always gotten what i want. I will never curse somebody out, but in the future if somebody tries ignoring me when i say lets not waste time doing that i am just going to tell them its not working out and i won't pay, they can delete the session.
I wouldn't be rude if i was working with you Monkey, but i doubt if i said "How about trying some echo on the voice here" you would say "No, not even going to try it, it won't sound good". By all means if you are doing something i like i wouldn't be opposed just because its not my idea. I didn't mean to come across super abrasive, just a sore spot because i have lost a few grand in bad situations
and its my fault for not being assertive.