Similarities that may exist between two sets of circumstances do not necessarily translate into anything that can be proven. One might state that all analogies are false when used to reason. Analogies may be very persuasive. In fact, we build many of our categories through analogy. For example, we might note the following.
People sit in beanbags and drink coffee, just as they do with regular chairs.
But they seldom go to sleep in a beanbag although they often go to sleep in a bed. Therefore, a beanbag is more of a chair than a bed. There is a form of reasoning called case-based reasoning which attempts to be formal about analogies and to draw on the observance that in fact this is how many conclusions are reached. Then, we might decide to do what we did when C occured last time, but remain aware of some of the implications that arise when B occurs. However, analogies are often used intentionally, in combination with other appeals, to support claims that are otherwise fundamentally unsound.