When we don't have any way of knowing what existed before the Big Bang or what it consisted of, an honest stance expressing our ignorance is warranted, don't you think?
What evidence, beyond erroneously applying "cause and effect" to the time before the Big Bang, do you have for this?
Time had a beginning point and, thus, exists (
http://www.hawking.org.uk/the-beginning-of-time.html). It doesn't exist in the linear way we all assume, but I never claimed this anyways. According to the best scientific theory we've got, time began at the big bang.