Jiraiya, AKA the Pervy Sage, is beloved among the Naruto fan community. However, despite his popularity, Jiraiya is actually a pretty terrible person.
His perverted behavior generally comes across as disturbing, as opposed to hilarious and lighthearted. And it's not just his predilection for peeping on women in the bath, or the fact he's aroused by a 12-year-old's transformed body. He also neglects important responsibilities and can be shockingly callous and cruel.
The fact that Jiraiya is a deeply flawed person does not necessarily make him a bad character. It's perfectly reasonable to like or even love a fictional character who does reprehensible things.
Jiraiya fans don't necessarily condone his perverted, irresponsible behavior—heck, even if that's their favorite thing about him, it doesn't mirror real-life attitudes. Good characters embody a combination of flaws and merits, and Jiraiya certainly does that. Even so, some Naruto fans still can't stand him.
For those who love Jiraiya, these moments might provide some insight into the depths of his depravity; for those who hate him, it can reveal some concrete reasoning.
Naruto's parents, Minato and Kushina, had such deep and abiding respect for Jiraiya that they named their son after a character in one of his books. They also chose Jiraiya to be Naruto's godfather.
The responsibility of a godfather varies depending on cultural context, but one thing is clear enough: it involves raising a child, or at least finding appropriate accommodations for them if their parents are not around to do so.
Despite this, Jiraiya had absolutely nothing to do with Naruto until the boy was 12. As a result, Naruto grew up experiencing crushing loneliness and isolation that left him with permanent emotional scars.
Did Jiraiya have a good reason for leaving? Sure—he had pressing professional obligations outside of parenthood, and he was likely dealing with some serious grief after losing Naruto's parents, who he loved dearly.
Still, there's no excuse for abandoning a baby he promised to take care of. If he didn't raise Naruto himself, he should have at least made sure someone else would.
At one point while Jiraiya is training Naruto, he steals the young ninja's coin purse in order to pay for alcohol and escort services. This is pretty bad, but if you look deeper, it's actually even worse than it seems.
Naruto is broke. As a low-ranking ninja, his pay is negligible. While he does receive a stipend from the government to pay for his survival, that likely isn't very much either. All the money he had in the world was in that coin purse, and Jiraiya took it to pay for his personal vices.
The paltry sum Naruto had saved was likely insignificant to Jiraiya, a self-sufficient adult with plenty of well-paying work. He didn't need that coin purse, he just stole it because he could.
One of Jiraiya's favorite activities is spying on women while they're bathing. This is played for laughs, but it's extremely repulsive. Besides being offensive and disrespectful, it's also threatening. Jiraiya often peeps on younger women who are less established in the community. He's also constantly making sexually inappropriate comments.
There's little anyone can do to stop or redirect his behavior; because he's in a position of power, his treatment of women is written off as mildly annoying at best.
Jiraiya never sees a problem with his behavior—he actually prides himself on how often he gets away with spying. It's hard to overlook his misogyny when he's never apologized for it.
The scene where Jiraiya leaves the orphans he'd been raising and training for several years could have been heartwarming (and in the anime, it is for the most part), but Jiraiya comes across as a total creep in the manga.
Jiraiya tells Konan she's going to be beautiful when she grows up, and that when she finally turns 18, she should look him up. In context, it's obviously intended to mean "when you're legal, lets hook up."
Not only is Konan currently underage, but Jiraiya has just been raising her like a daughter and is about to abandon her in a war zone. His reaction is totally gross, and also a pretty brutal way to make sure she knows their relationship is over forever.