Or, to put it differently, when Buddhists use the expression "selflessness" (at least in the West; Buddhist-inspired countries have much more preciser words), they don't deny that the self exists. They don't deny that it doesn't exist, either. What they deny is that the self
exists by itself, i.e. that it has some "eternal" property which is uncreated. This is confirmed empirically through experience, not a philosophical point to be accepted or debated, although knowing what to expect and what method to apply to validate that experience empirically is part of the (many) Buddhist methods and techniques.
As for the Buddha being an "emanation" of God... well, to be honest, Siddharta wouldn't really get angry at that explanation

He would just say something like "Whatever is helpful to you to keep a connection with me is fine. Sooner or later, if you have a connection, you'll be able to learn my methods and follow them". This is the reason why so many Buddhist schools explain Siddharta differently. For many Theravada schools, he was a "special being", and while he taught a way to completely erradicate suffering, you cannot "become" like Siddharta. For many Mahayana schools, by contrast, Siddharta was just a normal human, and by applying his methods and techniques, you can reach precisely the same state of enlightenment as Siddharta did — it just takes time (and many rebirths!). For many Vajrayana schools, the special technique that Siddharta has applied to attain enlightenment in just a single lifetime is freely available to all of us — it's just a rather dangerous path to follow, because it has lots of pitfalls. So which one is right, which one is wrong? The answer is: all are right. The important thing is that you start with a connection, which then leads to be willing to learn any of the methods that Siddharta taught. If that connection requires one to "believe" that Siddharta is the emanation of a god, then, fine, that's ok, so long as it means that thanks to this "belief" you're now willing to engage in the same path that Siddharta followed, because you're convinced that it's the only way to get rid of suffering. In fact, a lot of so-called Pure Land Buddhism schools have a completely theistic approach — their followers are aware that they need to believe in a "god" of some sort, so they view Siddharta (and other Buddhas) just as "gods" from which they request blessings, because they have "faith" that somehow this will put them into the right path to end suffering. And, in fact, they're quite right — sooner or later, no matter what idea one has of Siddharta, as long as there is a connection forged with him, one will be able to find a method that one is able to apply, and this will ultimately lead to the same state as Siddharta attained. It's really just a question of time.
An interesting aspect is that a "connection" doesn't automatically mean a "good" connection — in fact, even a "bad" connection is excellent! So someone saying, "all Buddhists are stupid and Siddharta was an idiot" is going to advance much faster than someone who never hear the word "Buddha". Sooner or later, even the rejection of the Buddha will leave a mental imprint, and in subsequent lives, that mental imprint will work out towards one's advantage in being willing to learn a bit more.
And if you want to discard any possibility of rebirth... well, it works in one's lifetime as well. For some unknown reason, I sort of came across some writings of the Dalai Lama in my teens, and they didn't make any sense at all. When I tried to find out more about Buddhism, I just came across the many anti-Buddhist pamphlets written by Christians, so I shrugged them off as some sort of nihilism, even though I couldn't really pinpoint that label on the Dalai Lama — he certainly didn't
behave as the nihilists I knew! But I said, "it's not for me", and never thought about it again.
It was only more than a decade afterwards that, by chance (or perhaps not!), a Buddhist centre opened just behind my street. At the beginning, we just said "hi" to our new neighbours, exchanged some pleasantries, and even gave them some Christmas gifts, as we tend to do to the neighbours. But there was no "impulse" to get mixed in their hocus-pocus, as we thought about it at the time. It was just when my wife was slowly recovering from a very serious panic attack that her therapist told her that meditation might be helpful. Since the Buddhist centre behind us gave free meditation classes, we thought it was worth a try. At that point, I was not interested in meditation at all (a few years before that, I had tried some sort of esoteric Christian meditation and it had absolutely no effect), much less in "Eastern" things, but obviously I felt that anything that would encourage my wife to get better was worth the effort. Besides, we were by then sort of familiar with the neighbours, and pretty much confident that they weren't sacrificing goats in their backyard or running around naked under the moonlight

but, instead, that they were easy-going people with a keen sense of humour.
So one might ask... what made us go to that meditation class? Was it merely chance? No... because there are hundreds of neighbours in our place, and almost none of them ever showed up on a class, even though all, without exception, have established some sort of friendship with the meditation teacher and his wife. I'm pretty sure that what made me stay was the negative connection I had with Buddhism in my youth — thinking it was some sort of nihilism — and, as such, I was interested in confronting this teacher with "my" views and "my" opinion of Buddhism, and see what he would answer. So there was a mental connection established by then, even if it was a negative one. I never thought in my life that I would
find a Buddhist teacher in my country — there are really very few around — but when I found one, I was eager to debate with him "my" views. I'm pretty sure that if I had never read anything about Buddhism — even those anti-Buddhist pamphlets! — I would never had developed any interest in Buddhism at all, just like all my neighbours, who are completely indifferent to Buddhism (but now they have established a connection, too! So it will bear fruit sometime!).
To recap... it's fine to imagine Siddharta as some kind of manifestation of a God, or someone with super-powers, or an angel, or whatever you wish — even thinking of Siddharta as a scammer and a trickster! — if that somehow helps to make a connection which will, sooner or later, bear fruit: one suddenly becomes interested in confronting one's opinion about Buddhism with someone of Siddharta's lineage, and that's the start of following the path that Siddharta has followed

That's the reason why Buddhists will create statues, temples, and similar representations of the Buddha. Not as a sign of "veneration", but in the hope that someone seeing those things start asking questions, and, by doing so, come in touch with a qualified teacher. And that's why we write in forums, lol — with luck, who knows, someone might be reading right now these very words and ask, "what are Zenda and Sandra babbling about? Aren't they just inventing all these stupid things? Maybe I should find a
real Buddhist teacher and get some
real answers!"
If that happens to any of you, I would definitely rejoice!