The trouble is I don't believe that all, or even most of the people who told him to kill himself were teenagers. I have no problem believing that there are adults out there who also would have joined in.
The internet creates big pockets of social groups that have no consideration of age, race, social status, etc. There's an interesting side-effect of looking for validation from your peers when you don't know what those people are actually like. We can act more mature by looking up to a mature audience, we can look down on a less mature audience, or we can resonate with the values of a less mature audience. I went from Digg to reddit to HN mainly due to interests/content, but also because I looked up to the more mature audiences. Some people will stick to platforms where they are entertained by immaturity and seek those people's validation by mimicking them.