I think I agree with Squiddy, somewhat, in that the misogny was definitely a product of who he was, but I agree with you (and very much disagree with him) in that, given it was the form his issues manifested in and did so in such an extreme manner, and is terrifyingly not an uncommon view within our society (even if not taken to the extremes that he did), is equally as vital to consider/discuss (if not more so, as a result),
There are some key points which suggest that it is more. First, we have his insecurity about his height, stature, race, and
his belief that he lacked any talents. He valued appearance above reality and
in his mind, these made him different and made it impossible for him to fit in. In turn, he
hated these people who were taller, and better-built than he was. This initial spite precedes any indication of misogny, yet is something that he constantly refers to throughout (blond hair is another trait he envies), and 'vexed' him, partly as it made him believe others were better than him (fueling his insecurity), while also later serving as fuel to his hatred of women (as he believed women were attracted to taller/better-built people because he was incapable of acquiring a partner). Initially, he could overlook this, as he desired to become an
'obnoxious jerk' by relieving himself of his own sense of identity by
abandoning his own likes and identity to fit in with those around him who had attention, and were popular. He responded to any
perceived embarassment with great fury, completely lacking a sense of perspective.
Eventually, as puberty began, the popular thing to do was to
meet with 'pretty girls' and he hated his failure, and inability to do so, taking girls' apathy to him as a great insult, misinterpretting the reason for it as he disregarded his lack of effort, implied awkwardness, and spitefulness, for the 'status' of the 'alpha male'. From here, he focused continuously on his hatred from women and his blatantly extreme misogny developed further through
bullying, perceived (yet not actual) rejection, isolation, spitefulness, envy, greed, hatred for authority/rules, hatred for the wealthy, insecurity, delusions of superiority (and I know this appears to contradict with insecurity, but he was simultaneously both, somehow), without reason. He was desperate to belong with anything, hating Catacylsm because it
brought with it people who were popular and had lives outside of the game and had absolutely no sense of empathy,
being sad about the death of his step-mother's father but being pleased because it meant she'd leave. He viewed any arguments as a competition
to be won, which he did so by throwing a tantrum.
Now, of course, he was a misogynist, no doubt. He had a 'final solution' for women, he thought they should be caged, were 'mentally ill', drawn solely to status and were rejecting him in their refusal to hook-up with him, felt an entitlement to other women because of his status (and made get-rich-quick schemes believing getting richer was his only hope, as they'd never be attracted to him), constantly berated them as 'sluts' for having relationships with others, and viewed them solely for their sexual aspects. He objectified them. He felt robbed by women. He hated, and despised anybody with even an association to women. He didn't care for women as people (actually, come to think of it, he doesn't care for anybody as a person, only in how they relate to him). Ultimately, he murdered six people (I don't know if the roomates are included in this number as I've seen it presented in both manners) and wounded multiple others. While he was extreme, some of these disgusting attitudes are prevelant in society (the 'slut' women, and 'player' men is a particularly toxic and disgusting attitude).
The misogyny needs to be focused on. It is crucial, and central to him. It has just as much importance as the numerous underlying issues, but I think it would very much be too dismissive to consider it as the only thing. Such a spiteful person, who constantly believed he should have been the best, who felt a catharsis in driving to buy a lotto ticket which he had willed to be 'the one', who fantasized about flaying others, being the dictator of the world, being envied by all, recoiled to even the slightest embarassment unproportionally, was unable to relate to anyone, was completely self-centred, hated and fought against any rules, and saw everything as a slight against him (even simply not smiling at him was a grand injustice) was never going to have a happy life without severe intervention from an extremely young age, and given that he actually had psychiatric intervention repeatedly, I really don't know if anything could have been done. Were he not to focus his hatred on women, it could have been authority, it could have been those in the past who 'wronged him' for the crime of being popular/having friends, it could have been against the bullies, it could have been against those of different races (although he is racist already), it could have been against his friends, it could have been his parents, it could have simply been himself, it could have been anyone that he would blame for not being flawless, and the greatest person to ever live. In fact, he states as much, that he would get revenge on anybody who
insulted him as he was a fighter, and even sought revenge on
his friends, even if virtual, for long past apparent transgressions involving not inviting him over while they were playing at times (despite being open about it). Ultimately, however (as you are suggesting), it was against women. He was misogynistic, and he blamed women for all of his failings. We could speculate about anything that could have happened, but this is what did happen, and he reinforced his views through the internet, media, and historical reading, his flawed perception of events, and his spite. Underlying issues are important, certainly, but his misogyny is equally as important (particularly, as mentioned, because of the prominence), and it seems unwise to de-emphasize just how significant it was to him. EDIT: Also, since it's been noted, he was mentally ill, or had a personality disorder, or had something incredibly wrong with his perception of the world from a very young age, but he, ultimately, is one hundred percent culpable for what he has done, and the hatred he spewed. I don't think it's fair to state that acknowledgeing mental illness is suddenly hand-waving him of responsibility and shutting down all avenues of discussion (but there are, certainly and unfortunately, people who are doing that, this I can agree with).