I never thought of this as a "quote", since it doesn't come from any famous source, but I live by it. I have, in fact, used it at the recess point of a dispute with a friend. Some background for it, though, to explain why it means so much to me.
My father was a preacher (none of that hellfire-and-brimstone bible school crap; he came out of McGill in 1927 with Masters in "Religious Studies", which nowadays is classified as "Theology". He was an agnostic. Together, we got mandatory religious education kicked out of the Ontario school system.
Anyhow, his two best friends down there were a screwy little Welsh dude who was the United Church pastor about 100 metres from our place—the entire community consisted of 2 churches, 2 cemetaries, a kindergarten, 5 houses, and a garbageload of orchards—and a severely religious Anglican priest. (My dad was Unitarian-Universalist, but Agnostic nonetheless.) John, the United Church dude, thought so much like my old man that they traded audiences (alright,
congregations 
) in summer. We'd go on vacation, and dad's flock would go over to John's place. When we got back, John and his wife would bugger off, and his crew came over to listen to dad. Such did not occur with the priest, but they loved razzing each other for hours on end.
So, to make a long story short (and yes, I know that it's far too late for that), the priest came up with some sort of terminal cancer. My dad made a point of visiting him in the hospital at least once a day, and even then they were scrapping in their usual friendly manner. One day, though, he decided that enough was enough and packed it in. The last thing that he said before he died was to my dad, and it's my favourite motto to this day:
I would rather argue with an intelligent man than have a fool agree with me.
This is a very long thread, and I have a very short memory, so if I've already posted the forgoing I beg your forgiveness for repetition. (I know that I related it
somewhere on PF, but I can't remember where.) I simply can't read through the whole damned thing to check on it.