Ronnikins took that surprisingly well, considering the blow-up over Hermione's friendship with Viktor at and after the Yule Ball.
The thing that bothers me about Hermione's character in canon is how she tends to overreact to anything Ron says to her. Sure, he tends to open his mouth, insert his foot, and chew vigorously, but I would think that by at least third year, she'd know him well enough to know he's not exactly the epitome of eloquence. She didn't go off as badly here as she could have, though, which helped Harry to diffuse the situation quickly and without devastation.
Teenage insecurities. To someone my age, they seem rather silly, but to a teenager, they're serious business. Even now that Harry's declared his feelings for her, Hermione's still a bit unsure. Perhaps once he sucks her tonsils out, she'll realize he really cares for her above all other. Well done!
Author's response
He did take it better than I'm sure a lot of people expected him to. My reasoning was that he realized that if he went off this time, he risked damaging not only his friendship with Hermione, but with Harry as well. That is why I had him hold back.
I agree; while Ron frequently says insensitive and/or foolish things, Hermione has a tendency to make things worse by overreacting. She should know him well enough by now to not take everything he says to heart. In this case, Harry intervened and played peacemaker with success.
Teenage insecurities, indeed. Having her tonsils sucked out may not ease Hermione's doubts entirely, but Harry will certainly give it his best shot!