I think one of the most interesting things about the 40k community is how one single opinion changes possibly the entire way someone reads most, if not all of the books detailing the Horus Heresy. That opinion being whether the Emperor is a force of "good" that tried and cares about his sons, or a force of "evil" that never cared and only created the Primarchs as tools. Angron is my go to example for this. Most Emperor "sympathizers" hate him, while the "haters" understand him. Would you agree?
Oh, this one is difficult. All I can say from now on is only my opinion, so must be taken with a grain of salt.
The Emperor is already a very complex character for many reasons and all about him is like talking about Alpharius, it can be true as it can be false, for even in the books there are various and opposing ideas about him. Also, the authors themselves have differents views of him and this make everything more complicated to us, the readers.
Not that I hate it, it actually helps making his character more and more mysterious and, you know, legendary-like. However, if someone only read a certain author's books, he will start to see the Emperor as that author wrote him, without seeing all the other sides that are described by other authors. (And I can guarantee that some writers will make you hate the Emperor so damn much, while others give you a more neutral pic of his character).
Then, his character not only changes between the different authors, but it has changed even during all this years. Very lately the HH's books have pictured an Emperor that actually loves his children, that wanted to save them from chaos, that was utterly happy when finding his first son, and that actually cried when Malcador dies. All of this now, when in 2016/2017 we got the "You were all just toys to use and then throw away" (Dark Imperium, by Guy Haley, and Master of Mankind, by Aaron Dembski-Bowden).
(Also, let's not forget about his "power" that people just see and hear what they want to see/hear when talking to him. This is why not everything we read can be accepted as it is written, because if he was talking to someone that hates the primarchs, they will only hear - and we will only read - : "they are toys, I don't care about them")
I entered this fandom only recently, like 3 years now, and I've read many, many books, but it's pretty much impossible to read them all, unless you're really into the full universe of Warhammer. So, this for telling you that I'm not and I'll never be the super-bearer of knowledge about warhammer, however my idea about the Emperor is basically this: he's an arrogant piece of shit and a terrible father, but he actually wants to do what it's best for mankind and he actually cared for his children. If he rarely shows it it's only because they are already grown-up men and he wants to treat them like such and not like babies, also he was trying to not show favoritism to any of them - to a point of course, he's still a man - and he had shit to do, that's why he was rarely present into the primarch's lives. Also, I hate him for reasons, but I understand and support his idea for a better future for humanity.
This is what I got out of the books I've read, but someone may have different opinions about him sooo sorry for the long post(눈_눈)
