SJS – the topic is taboo for one simple reason: The teachers and rabbeim that you ask do not know the answers (or even the questions). Rather than saying “I don’t know but you can ask so and so” they tend to brush off the questions one way or another.
I agree, these topics should be discussable. There exists no question that cannot be answered properly. In fact, some of the theories (such as the expanding universe theory related to the BB) logically leads to the idea of a Creator (the expansion had to start at some point). But I also agree with areivim – these topics are very complex and should be answered thoughtfully and carefully – NOT in a public forum. Books have been written addressing these questions, though.