Warning: contains major spoilers for X-Men: The Trial of Magneto #1!
There have always been a few problems with Magneto and the way he treats the women in his life. X-Men: The Trial of Magneto #1 reveals the consequences of his actions toward not just Scarlet Witch, but also his own daughter. The backlash he is currently facing has been a long-time coming.
From derogatory name-calling like "the Pretender" to forcing her to be used as a pawn at his whims, Magneto hasn't had the best relationship with Wanda Maximoff. Furthermore, the continual back and forth of their being related or not has often come from Magneto himself - calling her his daughter, when it has varied in truth and may have been a lie from the beginning.
X-Men: The Trial of Magneto #1 has the creative team of Leah Williams, Valerio Schiti, Edgar Delgado, and Vc Clayton Cowles. In this first issue of Magneto's latest scandal, both Lorna and Pietro turn on Magneto immediately when all evidence points to him being Scarlet Witch's murderer. Instead of believing that this patriarchal figure could be innocent, they believe without hesitation that he is likely responsible - and it's his own fault because of his misogyny.
Early on, Magneto mistreated Wanda - even before she was said to be his daughter. While a part of the Evil Brotherhood of Mutants, the Scarlet Witch was mistreated by her teammates, as well as their leader. She was targeted for her beauty. In X-Men #6, Magneto is trying to recruit Namor the Sub-Mariner. He thinks the best way to get the upper hand on him joining them is to use Wanda. Magneto practically throws her at him, but Namor doesn't join. In fact, he becomes angry with the Brotherhood's leader because of the way he talks to Scarlet Witch, stating that he won't ally himself with someone who "speaks to a female as YOU do!!" Namor is one of the most arrogant heroes, but even he knows that Magneto mistreats Scarlet Witch. Later on, in Avengers #110, Magneto takes control of Wanda and several of the Avengers. However, Scarlet Witch is the only person he makes do ridiculous things under his control, forcing her to dance for him and his own amusement. The other Avengers are left standing around, mindless, but not toyed with.
If older appearances weren't enough, Magneto's callous treatment of Scarlet Witch continues in House of M #7. With the Avengers after Wanda, Pietro is concerned for his sister and expresses his concerns to Magneto. Yet to Pietro's horror, Magneto doesn't seem to care about a terrible fate befalling her. He actually seems to agree with them. Eventually, Scarlet Witch causes numerous mutants to lose their X gene, and therefore their powers. However, not before she calls out what Magneto's decisions have done to her and Pietro. He never treated them like a proper family, instead choosing his cause over them and their well-being.
Magneto's misogyny and negligence have collectively led up to this exact moment. While it isn't surprising that Pietro would side against his former "father", it seems particularly tragic that his own true daughter, Lorna, wouldn't be able to side with Magneto either. When she comes after him personally, he calls her "unhinged" and "inconsistent", while she points out that the wives and daughters he has had end up being left in a path of death. She claims he tries to make them more willing to bend to his will and how he tried to break her without success. Magneto may be reformed now, but his decisions and actions prove he hasn't made up for his past misogyny.