Everything which begins to exist has a material cause. That's the only statement that is supported by observation or empirical evidence. Premise 1 either refers to material causes only, or it is completely undefended. The conclusion however wants to have an immaterial cause. An entirely different thing. The Kalam argument abuses the ambiguity of the word 'cause'.

The argument is also guilty of special pleading. It makes the entirely unwarranted assumption that God himself is immune to the infinite regress of causes. If it's okay to simply assert that, I could also assert that the big bang singularity, out of which the universe came, represents the first cause.

"Begins to exist" is also used equivocatory. Kalam proponents want to conclude that God made the universe exist ex nihilo. But everything around us only "begins to exist" in a trivial sense, as rearrangements of preexisting, uncreated stuff. Since the universe would be literally the only example of something truly "beginning to exist" from a previous state of nothingness, this means there is a sample set of one in this category, leaving no inductive support for the premise that "whatever begins to exist (ex nihilo) has a cause".

Further, premise 1 refers to things that begin to exist within time. In other words, there was a time when a thing did not exist, followed by a time when it existed. But this is probably not the case with the universe, since as far as we know, time is part of the universe. Our current understanding is that the universe has a finite age (13.8 billion years), and because time did not come into existence until after the inflation began, there is literally no time at which the universe did not exist. It has existed at every point in time. Once again, equivocation is at play. Premises 1 and 2 are comparing apples and oranges. The universe has existed at every moment in time and did not begin to exist in the same way that every object in P1 began to exist.

The Kalam is also guilty of committing a fallacy of composition. P1 declares that everything that begins requires a cause, and P2 goes on to place the universe at the same logical level as its contents. The first premise refers to every "thing," and the second premise treats the universe as if it was a member of the set of "things." But since a set should not be considered a member of itself, the cosmological argument is once again comparing apples to oranges. Describing the way physical objects within the universe behave relies on induction and physical laws, neither of which apply in the absence of a spacetime universe. Everything we are familiar with is an object within a set (the universe). It's a fallacy of composition to assert that the properties of things we are familiar with (objects within the set) are also properties of the set as a whole (the universe). Example: "Each part of an airplane has the property of being unable to fly. Therefore the airplane has the property of being unable to fly." The conclusion doesn't follow because the only way to determine whether the airplane has the property of being able to fly or not would be to get outside the plane (set) and then make observations.