One bad apple sure can spoil others in the basket. A friendly botanist can explain the process: plant tissues communicate using classes of compounds called hormones. Though these hormones are produced in one location (ergo, the bad apple), they can have an effect on target cells in a non-adjacent location. So our over ripe, bruised apple goes about her plant business transferring the hormone ethylene as a gas to the neighbors.
Have you followed financial advice given by a professional, friend, or brother-in-law (possibly all the same person) that turned out to be ‘bad’? Really bad? In addition to whatever financial consequences you experienced, did you decide that professionals, friends or brothers-in-law were not to be trusted to give financial advice? Or did you learn the important lesson: to trust yourself to identify the good apples?