After reading the article link, I have...mixed feelings about it. At best.
The author brings up some good points. I understand them, at least, even if I don't fully agree with all of them. However, he/she is wrong in a lot of areas as well. The points about how Buffy's life is so awesome just doesn't make any sense, and completely disregards, or doesn't even attempt to listen to, much of Buffy's character development throughout the entire series. It's just, in my view, wrong, and shows zero understanding of the character. Being the Slayer is not this awesome, super fun job. I mean hell, did the author even watch S2? I read a few of the comments below the article where the author launched into a number of tirades against people who disagreed with her/him. I've never really been a fan of people like that. It's always struck me as very odd to write an article or blog on a topic you're opinionated about, and then not want to even consider other viewpoints. That's arrogance, plain and simple, and nothing more. He makes several great leaps of logic in just deciding what the hardest things in life are, and stating them as fact, not opinion. And his "logic" of "Buffy's hot so she should be happier" is just, I'm sorry, childish idiocy.
Back to the article itself. I'm not saying "Earshot" is a well-written episode, but the question you asked of why should Jonathon care about how others feel is exactly what Buffy said, only reversed. Why should others care what he feels? There's a difference between being a bullied teen and being afflicted with depression. A big difference. I mean, this is the same Jonathon who became a self-titled "super villain" in S6 to get attention and make himself important. The same Jonathon who altered the personalities of people who had saved his life numerous times in order to make himself feel big. Clearly, he's an over-dramatic person, and I think that's a fair statement.
And remember, Buffy gives Jonathon her talk when she still thinks he's about to shoot up the school, not just kill himself. That's overlooked in the article. If I was in her position, and I thought Jonathon was going to start killing people, I wouldn't have even talked to him, to be honest. I would have taken him apart. Now, he wasn't there to kill everyone, but she didn't know that, so talking down to him (which I would argue she didn't) is more than well-warranted.