A friend of mine was going to Vegas for the first time, so I prepared a basic strategy chart for him to use. He later told me that a pit boss, while allowing him to use the chart at the table, had said, "You know, those things are wrong half of the time."
When you think about it, this would mean that BS is right half of the time, which means the game would be essentially even.
But the dumbest thing I ever heard was said by yours truly on my first trip to Vegas in the early 70's. I had read John Scarne's book on gambling and was using his basic strategy, which is hopelessly wrong. Despite this, I was very lucky and ended up about $800 ahead, betting $2-$10 a hand. At one point after I had split 10's and won both hands, I replied to someone who had questioned my judgment (or my sanity -- I can't recall), "You should always split 10's against a 6!"