When the question arises about why Quagmire hates Brian, fans are quick to point to his comments in "Jerome is the New Black." In fact, u/Background-Factor817 posted the entire speech, with Quagmire touching on several aspects that any regular "Family Guy" viewer will instantly recognize about Brian. "You constantly hit on your best friend's wife, the man pays for your food and rescued you from certain death, and this is how you repay him?" Quagmire says. The reference is hard to miss, as Brian has long held an unhealthy crush on Lois, yet Quagmire seemingly forgets his own lust for Peter's wife.
Also, while Quagmire acknowledges that he dates women purely for their physical attributes, he remarks that Brian pretends to be an intellectual who's interested in women's minds when he's actually no different. "I don't buy them a copy of 'Catcher in the Rye' and then lecture them with some seventh-grade interpretation of how Holden Caulfield is some profound intellectual," Quagmire notes.
Not everyone approves of Quagmire's critique. u/serialkiller_mne recognized his points as valid but found him to be the last person qualified to judge another's actions towards women. "Quagmire is a literal rapist. He does way worse things than Brian, yet he had the audacity to lecture him," they wrote. It's a sentiment echoed by other users who point to his interactions with not only Lois but also Meg. The latter's age is especially troubling as she is just 18 years old.