Namely, that those habits "desensitize" them to the sexual experiences they "deserve".

Women say that men who watch porn have unrealistic expectations about sex. This is largely due to women in porn being far more attractive than the average woman, and providing the visual impression of sexual experiences out of the realm of possibility for the average man. This as a result makes these men less satisfied with the unenthusiastic sex they have with women on their looks-level.

Likewise, men who complain about the "cock-carousel" say it's unfair that 5/10 women can bed top-tier men who would never get in a relationship with them. If an average woman fucks a male-model tier guy, all guys she fucks after will be unarousing and underwhelming in comparison.