What makes you think you know what's best for him? I guess you probably went to college, but maybe you didn't. What I do know, is that you didn't both go to college and also choose not to go to college.
If you did go, then you don't know what would've happened to you if you hadn't gone. You could have lived in Costa Rica for 3 years and decided to establish a charity, never thinking twice about the value of higher education. Maybe later you would've posted in this thread, and had the top rated comment about how much you learned on that trip in comparison to what your friends learned in college.
However, it's also possible that you didn't go to college, and are simply regretting that choice and trying to warn those younger than you not to make the choice that you did. But what if you had gone? Maybe you would've hated it, and dropped out after two years, thinking it was a completely horrible idea.
Whether or not you went to college, you don't have the full picture. You don't know what it would've been like to do the opposite. That's why this is not an easy question -- that's why people actually talk about this. If it were as easy as "I'm older than you, and I think you should go, therefore you should go," this thread wouldn't exist. So don't act like you have the right to tell others how to live very important parts of their lives. We all have to walk our own journey, and make our own decisions, and if we just listen to those more experienced than us, we will never get anywhere important. And we probably won't be very happy, either.
The OP himself is trying to sway the argument with 'Appeal to Adventure' (not really a defined fallacy but appeal to emotion). For instance the call to take the blue pill is a reference to what the Hero of a very popular movie didn't do. The OP equates post college life with an un-heroic life.
There is a visible disconnect with the views in the arguments. They are more open and accepting at the start and get more emotional at the end. To state an example, the author mentions that 'school is in no way a negative experience...' and later mentions that 'Sure, school might maximize one’s chances of living a stable, moderately successful life with two and a half kids, a modest house, and a job. But is that really what we want? Does our generation want to forego pursuing our passions in order to be part of a shrinking, mundane “middle” class?', which seems to point that schools leave you passionless.
The OP also uses arguments that cannot be proved or argued against. For instance "Not that dropping out of school ensures success, but had Bob or say, Mark Zuckerberg, stayed in school, we could all still be hanging out on Myspace." What this statement assumes, is that (1) School didn't help Mark Zuckerberg, (2) He wouldn't have been able to build FB if he had waited to finish school (3) No one else could have come up with an alternative to MySpace, university student or otherwise. I am not dissecting the argument just for the sake of it, but I am arguing that the OP is selective about his dataset. Yes there are Mark Zuckerbergs, but there are Larry Pages as well.
I think it's an ad hominem attack only when the character assertions bear no relation to the argument at hand. In this case, for him to call the OP young and ignorant is perfectly relevant, the implication being that he only dismisses higher education because he is not experienced enough to realise the value of it.
It's not relevant to the argument if there is only a weak implication that going to University would change the ignorant part, not to mention that he provides no backing to the idea that if you go to college you will "grow up" and become less ignorant. This smacks of a circular argument without actually evidence.
His criticism isn't about the OP's lack of time at University, it's about his lack of life experience. I mean, the guy's a sophomore at college, after all. It's not outrageous to suggest that he's a bit naive and/or idealistic.
He doesn't need to provide a "backing for the idea" - Holloway's point did that adequately. And for me, personally, reading the counterpoint just convinced me of the validity of Holloway's argument further.
