This is one of my favorite episodes and the reasoning for that is all about Giles. As far as the question at hand... he is the one Scooby that doesn't get in her face, for that matter he is very leniant in my opinion. That plays a part in the story that is telling to me. Giles handeled it as a mature collected person seeing both sides, I still almost cry when i see him almost crying at his excused exit to get the tea. He handeled it both like a watcher and friend, and gets bonus points for the best line of the episode "Don't you like my mask? Isn't it pretty? It raises the dead!....Americans."
As for the rest I'll try to explain where I think they are coming from:
Joyce sort of angered me in this episode, but I could somewhat understand why she acted as she did. There are no two characters in this episode closer than Joyce and her daughter, yet she joins a freaking book club when Buffy goes missing for what.... 3 months?!? She doesn't recall the ultimatum she gave Buffy and feel responsible for her absence...or maybe she does?
In her defense, she was dealing with the whole super power thing and her daughter being in continual danger, and thankfully as a parent I don't know what thats like- completely- but I imagine that would make you irrational and do things to 'protect' you and yours.
Joyce seems to always try to inject normalcy into her daughters life....maybe the book club and taking the disappearance so lightly/assuming that her daughter had run away as opposd to being kidnapped or killed by Vampires/what not.... was just her way of continuing to do so? To protect herself, to insure herself Buffy had in fact ran away and would come back....or at the very least was still alive. Her anger gets a pass at any rate, it was the other behavior that made me stop and wonder where the writers were coming from. (As usual it made sense)
Oz gets no pass for being the cool one, as he has his own inner deamon to contend with and is new to the scoobies and I honestly think he lets Willow talk for him in this case.
Xander is angry at Buffy for a reason besides her making him become "Night Hawk" and putting the crew in danger by shirking her responsibilities.. Lets not forget what he told Buffy about his intrest in Cordy in a prior episode, he says something akin to....the only other girl I'm interested in is taken. Taken being Buffy...plus remember what how Buffy treated him in "When She Was Bad" in season two's opener? Xander is still somewhat in love with Buffy at this point, at least I think deep down he is. (Lets face facts, in this season his love for Cordy gets comprimised, who's to say Willow is the only one who could do that?) I think he feels rejected, much like Willow does, but more so. He thinks that not only did Buffy not have faith in him as friends to deal with all she had gone through at the end of season two, but she also did not have any faith in him at all. I think he felt abandoned and not good enough on a whole other level than Willow, thus he was a butt head more so than her. Women don't have the market cornered on the whole lover scorned deal.
At the same time, what other posters have said is very true; he was very worried about her and probably resented the 'stupidity' of her actions putting them all in danger when she bailed.
Onto Willow.....Willow said it best 'You were my best friend' and then she had to deal with life without Buffy. She saw in Buffy a role model, an uber person, but most importantly another person other than Xander. Xander had been her friend for how long, yet Buffy gets the digs of 'Best' in two seasons? I can't say why except that perhaps Buffy acted as a filter for Willow to understand/cope with her old feeling with Xander. She could not exactly talk about her feeling for him to him. there are all those changes she was going through too, like falling in love with Oz and coming socially into her own. She was left with Buffy's responsibilities and a new social life to contend with alone too, all beacuse her hero and friend fell from grace in eyes by making a monumental mistake, one she caught her repeating....thus willow reacted as she did.
As an observer it is easy to say they were to harsh, but thats what makes it so real despite the vampires and why i espeacially love this episode. How many people are we too harsh on before the days end during our lives? To an outside observer anyone can be a jack-bag because they can not feel what the person they are judging are feeling.
Were they two hard, I'd say yes. I think giles handeled it best, Joyce too, all things considered.
Xander and Willow reacted like i would knowing what they know, so even if it was harsh, i could certainly understand where they were coming from.