Really? I've found that being good at logic (and good reasoning in general) makes me a lot worse at convincing others, because my motivations for believing things depart so much from theirs.
I guess it depends on what industry you are dealing with and on what level. When you are dealing with Hollywood, they tend to pull out ALL the tricks. Protection and savviness on business deals is a must. Its an aggressive world out there and if you are going to take your business out of doing family and friends business, you may need to be prepared for sharks. We have done contracts within many very competitive markets and it can get aggressive out there.
You deal with sharks by beating them at negotiation and people skills, not by beating them at logic. Logic is a defensive weapon only--it keeps you from getting fooled, but it won't really sway others.
Good point about "it keeps you from getting fooled". Thats a serious conclusion you make, and however you needed to get there, Im glad you were able to finally arrive at my main point. :)