I'm a 4th year University Computer Science student, and I have this problem, that I don't seem to be able to find a straight answer to:

As a 4th year computer science student, I spend more time in the computer lab on campus, than even my own home. This means that getting along with everyone else here is very important to me.

In most cases, this is not an issue because my interactions with almost all the people here fall into one of the following categories:

1. Let me help you, junior
2. Hi fellow student in a course I'm taking, I'm having trouble with this assignment question. Can you give me a hint as to how you solved it?
3. Hi fellow student in a course I'm taking, This is how I solved the problem that you're stuck on. Hope it helps
4. Hi fellow student, I noticed that you're working on a project, using a library that I'm interested in. Can we setup a time so I can learn about this library from you?

This model of interaction works very well for me. However, there is one fellow student, who manages to make my life hell beyond all of this (his name is not important, let's just call him "Sam").

He seems to be always (pardon my crass description) high and completely unwilling to contribute to a constructive, academic conversation. He's a pretty smart guy, but just comes across as (I hate to say something like this about a fellow student, but) an imbecile.

He also has ignorant opinions on important topics, some of which pertain to my specialization (AI, NLP, etc), and when I try to explain to him why he's wrong, all he does is insult me and put me in a foul mood.

I have tried ignoring him (sitting somewhere else in the lab, headphones, etc), but he seems to like doing this because he approaches me and no amount of "leave me alone" seems to do the trick.

Can anyone please suggest to me how to deal with this man in a civil way?

Thank you