Self Contradictory atheism/science

Science insists there must be a 'reason' for everything. Yet when asked for the reason that existence came into being, they say you do not need a reason. How can we argue from this position?
Atheist Answer: 

I'm assuming you mean that everything must have a cause.

Even science isn't so solid on causes anymore, having so far failed to find a cause for the probabilistic quantum mechanics of particles even while predicting them to within microscopic distances.

But let's assume everything generally does need a cause. If it's unreasonable to say that the universe doesn't need a cause, how much more reasonable is it to say that its precursor, its cause, doesn't need a cause itself? Is an eternal universe harder to imagine than an eternal god?

If we assume anything with a beginning needs a cause, something must be eternal and you can't escape that by putting in a god. At least we have some reason to suspect that the universe is eternal, as we know matter and energy exist and they can't be created or destroyed. Basic conservation law. Not really knowing jack about gods, we have no equivalent basis for their existence, let alone their infinite age. Given the initial assumption, I'm going with an eternal universe.

- SmartLX