It is true that big bang advocates seem to imply that something came from nothing. BBT does not go that far but the implication is clear. That means that the phrase "clearly wrong" is inappropriate. The correct phrase might be, "BBT does not describe precondtions to the observed expansion and so it is not a complete cosmology". Even if BBT is not right as far as it goes, it is not "clearly wrong" as it would be, for example, if it relied on supernatural causes for the Big Bang. Supernatural causes are not science. Natural: A natural cause (mechanism) must be used to explain why or how the naturally occurring event happens. Scientists may not use supernatural explanations as to why or how naturally occurring events happen because reference to the supernatural is outside of the realm of science. Scientists cannot conduct controlled experiments in which they have designed the intervention of a supreme being into the test. Tentativeness: Scientific theories are subject to revision and correction, even to the point of the theory being proven wrong. Scientific theories have been modified and will continue to be modified to consistently explain observations of naturally occurring events. If BB advocates apply the "tentativeness" concept of scientific theories in the future by adding language about preconditions that would not be currently testable, but that could conceivable lend themselves to future testing, you can bet that BBT will be modified to include protoscience aspects. "Emerging Science Defined: Emerging science (or "protoscience") may be defined as a "near science". A protoscience tends to conform to most of the criteria to qualify as science but typically falls short in one or more of the criteria. A protoscience differs from a science in that consistent observations and predictions may be limited by knowledge and/or technology. For example, let's look at parapsychology. This includes such phenomena as clairvoyance, precognition, and psychokinesis. Scientists generally consider parapsychology a pseudoscience because its phenomena conflict with known physical laws. However, at least one member of the parapsychology family, mental telepathy (thought transmission directly from one brain to another), might be worthy of scientific consideration. Mental telepathy, then, could be considered as a "protoscience"." This link presents one method of determining science vs. non-science which it refers to as pseudiscience.