Why do you not believe in God?

[Skepsis]

Care to give some examples of things that began to exist, and then some examples of things that didn't?

Well said.
If you cannot give another example of something that didn't "begin to exist", then you are essentially relabeling God. This makes the new Kalam more or less the some bout of special pleading that the old Kalam was, as it too suffers from the "Then where did God come from?" objection.
Relabling or redefining God into some semblance of a logical argument doesn't make him any more extant.

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I knew I read this somewhere, so I looked it up.

The curious clause “everything that begins to exist” implies that reality can be divided into two sets: items that begin to exist (BE), and those that do not (NBE). In order for this cosmological argument to work, NBE (if such a set is meaningful) cannot be empty[2], but more important, it must accommodate more than one item to avoid being simply a synonym for God. If God is the only object allowed in NBE, then BE is merely a mask for the Creator, and the premise “everything that begins to exist has a cause” is equivalent to “everything except God has a cause.” As with the earlier failures, this puts God into the definition of the premise of the argument that is supposed to prove God’s existence, and we are back to begging the question.

--- Iron Chariots Kalam Wiki entry on the circularity of such an argument.