Atheists, tell me, a Roman Catholic: why should I become an atheist?

[Tonus]

Actually this person feels that it proves God is highly likely to exist, and that "atheists are putting a great deal of faith in the tiny sliver of a chance that God doesn't exist."

Many of these arguments are intended to show that god is necessary. They are not intended as a direct proof of god's existence or to show what the likelihood of his existence is. The idea is that god has to be real or the universe doesn't make sense. But this relies on the gaps in our knowledge of the world and the universe. There may have been a time when lightning was indicative of the existence of a god, just like there was a time when it made sense that the Sun revolved around the Earth. We may never learn enough to eliminate all of the gaps that god can be wedged into, and so god will continue to exist in an ever-diminishing form for a very long time.