Without question The Phantom of the Opera is far more popular and I would say that a part of the reason is that its answer is easier for the audience. Erik is a violent sociopath stalking his sexual obsession and he follows a literary archetype of someone who society has wronged turning to the dark side. Yet, once he is on the dark side, the apartheid that society has made between them and him is entirely justified. Past generations are at fault because they didn’t have a valid reason for making Erik a pariah, the current generation has a perfectly valid reason. Erik’s sociopathy gives society a legitimate reason to screw over someone they didn’t like anyway.
Kafka’s The Metamorphosis is quite different because Gregor Samsa is not a sociopath and never gives society a legitimate reason to screw him over. The audience is made much less comfortable because it is harder to justify screwing over someone who isn’t a sociopath. All Gregor Samsa wants is humanity while Erik doesn’t want humanity, he wants to marry above his league and revenge. Denying humanity to a decent human is harder to watch than keeping a sociopath in prison which is basically how The Phantom of the Opera ends. Kafka’s The Metamorphosis ends with Gregor’s suicide after he overhears that his disability is a burden on his family.
Both have real life analogs in sociology and psychology but for every deranged incel with an AR-15, there are fifty lonely-ass, socially awkward, losers who watch the yuppies’ nightlife with FOMO and envy for the seeming richness of their human experience. They don’t make headlines and they usually don’t even join the toxic Reddit threads. They’re decent folks who spend their weekends alone and their speech impediments and mannerisms and even physical disablities make them hard to have conversations with and, perhaps, a risk to one’s social capital to be seen with.
The people who buy tickets to The Phantom of the Opera are the yuppies who want that message about the people they snub. They want the message that the losers are potentially violent and dangerous or are otherwise unsafe to help. It rationalizes their prejudices. I mean, they have the Rawlsian arguments and they can hyperbolize the how little in time and resources they have to cope with the problems of their social inferiors but, in the end, they have nothing that can sheild them from the reality of what they’re doing. Their class won’t afford humanity or dignity to the people beneath them. If the yuppies’ social inferiors violently wanted sex, that would be easy to answer. But most of them silently yearn for humanity.
I wish that the stories were flipped and Kafka’s The Metamorphosis took the place of The Phantom of the Opera. Both are counterparts and both are about having a disability. One is easy for the audience and reinforces what they want to be true. The other is about what is vastly more likely to be true. Everyone has a right to deny someone sex but does everyone have the right to deny someone humanity? I’ve touched on that topic and according to the Rawlsian thin-good, totally you have the right to deny someone humanity! It is the right of everyone to treat anyone like subhuman scum in a free country, according to Rawls, because the systems of virtue ethics and utilitarianism which would suggest otherwise would be “thick-goods”, tantamount to a state religion, and contrary to the spirit of liberal democracy. Giving more press to Kafka’s The Metamorphosis would challenge Rawls’ thin-good.