Anal sex is only for certain people with certain fetish. Only a small number of women feel truly biologically pleasant during anal sex. And for man, the biological pleasure is limited compared to oral and vaginal sex, but more about psychological pleasure such as the sense of conquering the female (a natural instinct for men).
mos555 explained the difference between love (e.g., constructive) and hate (e.g., destructive), which is accurate. I'd like to add on to this about
the difference between love and lust: the former is more
altruistic (e.g., self-sacrifice for the partner's wellbeing) and the latter more
egoistic (e.g., sacrifice the partner's wellbeing for one's own desire).
These definitions further prove that Kirito has love to Asuna, whereas Inoda only has lust. Kirito takes the responsibility to solve problems for Asuna so things can become easier for her, while Inoda only cares about satisfying his own desire.
Anal sex is an additional example. There was a time when Asuna asked Kirito if he wanted to try anal with her, but Kirito refused. This is actually understandable because Kirito loves Asuna, so he doesn't want to risk Asuna's wellbeing to meet his desire. Inoda is the opposite. He actively proposed to fuck Asuna in the anus, not caring about the potential risks for her wellbeing. For him, it's all about lust: satisfying personal sexual desire and conquering the female (especially Asuna from the upper class compared to himself).
In Chinese, there is a new phrase called "站起来蹬", meaning (literally) "stand up and ride". This phrase is used in the situation where a man has no love to his girlfriend but only wants to satisfy his lust, so he doesn't have to care about the woman's wellbeing but just "ride" her in any possible ways he likes, even though sometimes it can be harmful to the woman.
Putting together, Inoda has no love but only lust to Asuna. All he cares is to "stand up and ride" Asuna. In Chinese forums, some people say that Asuna deserves it, because she is hypocritical, betraying and hurting Kirito, who truly loves her.