Because of certain things said and done throughout Marius' life, fandom has created within itself a set of misconceptions about Marius' nature and his personality. While some of them just may be true, there are some that are most definitely untrue.
Marius is a pedophile
No. I think that people forget the nature of history. Things change, society changes, and values flow along and evolve with them. In Ancient Rome, Pandora was at the age where girls usually got engaged. NOT married. Men got engaged in their 20s and married; girls got engaged and married between 10-12. That was the nature of marriage. Condemning them now would be like people 2,000 from now calling you a pedo for marrying an 18 year old. And in the days of Armand, in Venice, it wasn't unusual for a man to have a kept boy. Marius was doing nothing against customs and values at the time.
Marius hates women
Very not true. Any comments that Marius made against women were not made with the intent of being a misogynist. So he said that intelligent women are threatening, he wasn't saying that women shouldn't be intelligent or that he feels intelligent women to be a bad thing. What people have to remember is that some of what Marius says in relation to women has its source in Pandora. Given the anger and the arguments that divided them, he would always refer to her with bitterness and harshness. Marius judges Pandora. Marius respects women and can't have his women any way but intelligent. If he truly found intelligent women threatening, he wouldn't love Pandora as he does, have felt so entranced by Eudoxia (even if he also thought she was insane), and loved Bianca.
Marius is a sadist who loves whips
In the Vampire Armand, it wasn't the act of whipping Armand that Marius enjoyed. Not at all. Marius was very serious and stern during the whipping. It was afterwards that Marius enjoyed. He enjoyed the blood, licking the blood. He's a vampire, not a sadist. Never in any books as there been moments where Marius has delivered pain with relish, unless perhaps he was lashing out in anger or revenge. Whipping was an act of revenge. Marius has said himself that he loathes the messiness and frantic nature of fighting-- it's inelegant. Violence is not Marius' nature.