Its really a case by case basis. I'm fine with some characters being abrasive but other characters get on my nerve about it.
I guess intent is an important factor. Why are they so abrasiveness? Someone like Felix has clear reasons for the way he behaves and when he calls people out he's harsh but usually correct in his criticism. Takumi and Severa are still essentially children and should be given some leeway while Shinon is just an irredeemable scumbag with no justification for his behavior and who's only redeemable if he's around Rolf. And while Sylvain does have reasons for why he acts the way he does he still deliberately sets out to cause harm and doesn't seem too bothered that he causes harm to innocents just as much as those who really do like him for his crest.
Shinon: He's just unpleasant all around. He's racist, he's an asshole, he's a drunk, he's a traitor and hard to get along with on the best of days. There's very little nuance here. There is no real reason for why he's just a scumbag. There are particular reasons why he doesn't like Ike but he's hardly any more civil to people not named Ike. I guess the lack of nuance just makes Shinon very uninteresting. He's just a prick and little else. He's sweet to Rolf but considering its Rolf I'm not going to give him much credit for that one.
Takumi: I have an easier time sympathizing with Takumi. He's obviously a brat but there are reasons for that. He suffers from multiple mental problems ranging from anxiety, to self esteem problems, chronic nightmares and more. Takumi's behavior stems more from being vulnerable rather than being malicious. Tsundere's being extremely aggressive towards everyone else just to hide their own self doubt often irritates me but in the grand scheme of things Takumi isn't even all that bad with this. He's not very hard to win over and when he's won over he doesn't revert back to a tsundere and force people to prove themselves to him. If Takumi's won over he's often very friendly, sociable and protective of them. Even his infamous snapping at Azura is quickly followed by the two being quite close.
Severa: Its to a far lesser extend then Takumi but I have an easier time cutting her some slack too. Still she does serve better as an example than Takumi of a tsundere tearing others a new one just because they refuse to be honest with their own feelings and that's not a good trait to have. On the other hand we also see her grow out of this phase during her time as Selena which is nice.
Hanna: She's just an absolute scumbag. There is no justification for blaming a kidnap victim for getting kidnapped. It did make Sakura sad but that's still Garon's fault rather than Corrin's. And in other conversations her ''I don't minch words'' typically just means that she's an asshole to everyone.
Hubert: Mister Vestra has one very important trait that makes it okay for him to be a jerk. He's fun about it. Being somewhat of a villain Hubert already has more room to be a jerk but he often is very witty, sarcastic or just fun about it. Hubert seems to be having fun with it, the ways he approaches it are often funny and so I have fun seeing him in action.
Felix: With him i'm more fine about his behavior because Felix is harsh but fair. The things he calls out aren't defense mechanisms or him overreaction, they are often very real. Dimitri really has an insane side, Dedue getting along with the insanity really can get very dangerous, his fathers priorities are massively out of wack, chivalry in Fearghus does more harm than good and Mercedes really was being patronizing, even if unintentionally. People who don't press any of Felix' buttons such as Annette typically don't get a tongue lashing and he's not above rephrasing himself to sound less critical such as with Ashe.
Sylvain: In contrast with Felix Sylvain is both harsh and unfair. He's more sociable to be sure but he also deliberately sets out to do harm. Felix doesn't get on people's case if they don't press his buttons but Sylvain is convinced every woman is out to press his buttons and so every woman is a target for him. All and all he's just very malicious about it.
Edelgard: Aside from trying to take over the world she's not so bad. She's definitely haughty and a bit arrogant but she's not really an unpleasant person to speak with. She's actually the only house leader who's on good terms with pretty much everyone in her house. Even her annoyance with Ferdie isn't nearly so hostile as the relations Dimitri and Claude have with their critics.