At this point, I only pop in on fandom discussions but I already see there is a very distinct and vocal faction of people who HATE this guy. When it comes to Type-Moon properties the main male protagonists tend to either be ignored or hated. Up until this point, Shirou Emiya was the fandom’s lightning rod of hate. He was so hated that I think he helped draw away anger from other characters. Soujuurou Shizuki and Mikiya Kokutou play second fiddle to their much more prominent heroines to the point that they barely register enough to get hate. I’m not sure I can’t even remember anyone having a strong opinion on Soujuurou. I’m sure people have opinions on him but I have never seen them. Shiki Tohno is pretty much the exception that created the rule. Fans liked his style of the protagonist so much they have not really taken to any other sort of main male character. Then in comes the character who eventually is known as Sieg.
As I have stated before I only know the broad strokes of the stories and characters of Fate/Apocrypha, therefore, I am a little hesitant to make judgments on any characters unless I am familiar with them from other Type-Moon stories. As an example at this point, I really know Mordred from other material but I can’t really tell you anything about Achilles more than you would get from reading his historical Wikipedia page. It does not help that most of the time people merely state that they really just hate Sieg. I’m sure they have a significant beef with the character I’m just not sure what it is. He is mostly a mystery with a vague cloud of resentment around him.
What I’m basically saying is that I’m going to try to go in and judge him as fairly as possible. I’m going to avoid mindlessly jumping on the hate train as much as I avoid defending him just because he is a target. If you hate the guy that is cool as long as you came to that conclusion on your own. Heck after watching this series I might be one of you. But if you really like the dude you might also take this as a bit of advice to avoid saying that publicly unless you are spoiling for an online argument.