While it's always healthy to be sceptical about things and to re-examine the evidence supporting your science, it seems a worrying number of people are taking this far too far. The bottom line is that there is a wealth of evidence that supports the Big Bang theory which no other known theory can explain.
What do Theoretical Physicists Do?
To anyone who is confused about what it is exactly that theoretical physicists do, here is a brief yet broad summary of what we're trying to achieve.