Re: "is Buddhism an atheist religion?"
YES, the Buddha explicitly rejected the idea of a "creator god", especially wrt his own teachings, and denied that any "salvation" (he spoke of "liberation", but that was also a very different thing) could come "from gods".
When the guy says, which buddhism do you mean?", he is addressing the many things that "Buddhism" has become since the Buddha died and Buddhism was largely swallowed up by Brahminism and co-opted into local superstitions and animism and re-branded. Especially, I would venture that he is referring to such things as the worst offender, the Tibetan religions, which have very little to do with what the Buddha taught. And I mean, a VERY, VERY little.
When he starts pulling out books -- I have those books, and those are what are almost universally (except for a lunatic fringe) recognized by buddhists and scholars of buddhism as records of the teachings of the Buddha.
He talks about disbelief in "a spiritual realm", and he is correct that, within the Buddha's own teachings -- the ones he called "noble, untainted, liberating", belief in such things had no place and was irrelevant.
The presenter mentions the Parinibbana Sutta and talks about gods supposedly taking an interest in the Buddha's death, but from what I have seen, he doesn't seem to take into account that the Buddha didn't give the Parinibbana sutta (a sutta is a discourse): it is a story about his death, which supposedly quotes him from time to time, but the Buddha wasn't alive after his death to give a discourse about his death -- someone else told that tale later, and injected their own superstitious beliefs into the story. Keeping in mind that many of the people who went forth under him came from a superstitious worldview, and that part of his course of teaching was somewhat of a gradual deprogramming from various superstitious beliefs, and many didn't ever completely or even partially let go of such beliefs before he died. His own cousin, Ananda, who is said to have memorized most of the discourses we see in the scriptures, admittedly didn't "get" the Buddha's teachings, and it is clear from many things Ananda says in the suttas that he never gave up superstitions and belief in karma and reincarnation.
The presenter talks about "Enlightenment" -- the Buddha never used that word or anything like it.
-- the "teacher of gods and men" phrase was a common compliment that was bestowed upon various wandering sages by people who were impressed with them. WRT the Buddha's own teachings, the phrase is meaningless.
He is correct in his assertion that the idea of gods is irrelevant to the "path and practice" the Buddha taught.
The Buddha didn't seem to bother with trying to argue outsiders out of their beliefs in various gods, etc. What he would do instead is take the beliefs a person he was talking to already believed in, and turn them into teaching tools in a way that would point toward his own observations and recommendations. But they were not a part of his own internal, liberative teachings. I think the presenter is basically trying to get at that point or something like it, and if that is the case then he is quite correct.