I knew a VC who you could describe as Barney Fife, and be 100% accurate. I always talked to him on a level he could understand, because I too thought he was a little slow. I was polite and explained things so that he understood how we where doing.
Fortunate for me though, I never was on the opposite ends of his ambitions, because he fooled everyone who crossed his path.
One day, we where in the process of negotiating an exit with a huge player in our market and I enter the room with him and our CEO (a brilliant guy), conversations start and this guy turns into Mr. Negotiator. I mean here is a guy that I have known for 2 years and all the sudden he is the smartest, shrewdest guy in the room. He is tearing apart arguments, quoting technical information that I explained to him (winking at me, saying that he was listening). Explaining financial models to them and why they wont work for us. etc. etc.
I walked away from that table with a totally different perspective than I walked in with. The moral of the story was sometimes the bullshitter gets bullshited. They thought they had this guy, and when the time was right he, let go, blind sided them, took them off of their game, and walked out of the room holding the aces.
I learned that day, that the dumbest guy in the room, may very well be the smartest guy in the room. Never underestimate people and their capabilities it may come back to haunt you.
After that meeting I said to him, man I feel like I don't know you at all, in which he said something pretty profound, he said: I am the same friend you have had for two years, and that is a humble good listener. Those last 3 words have been what I have aspired to be since that day.