How do I deal with this guy?

Here is the basic problem. You can't read his mind. He can't read your mind. So you are having a awkward social interaction where neither of you knows what is going on.

It makes perfect sense for a classmate to say "hello" to another classmate. I don't see anything that he is doing wrong there. If he is actually following you around, that would be creepy. It may be that he finds you attractive and is just trying to figure out how to talk to you (this is less creepy as long as he stops when he finds out you aren't interested).

But you don't know. Most human beings are decent... I think you should give him the benefit of the doubt. What you need is to have a normal social interaction with him.

My advice is that next time he says "hello". Turn around and say "Hi my name is Lindtxor, what did you think about the homework last night?". Have some friendly small talk so you can see that he is a normal, respectful human being.

There is a chance he will ask you out. That's a normal thing, there is nothing wrong with a man asking a classmate out. You can politely say "no thank you" (assuming you aren't interested). Then you have gotten that out of the way and he can be a normal classmate. There is a small chance he is a creep, but if he persists after you say "no" then you can go to the University for help. But normal guys will respect a clear "no thank you".

If he just wants to be friendly, then you can have small talk when you see him, or maybe even get feedback on homework or whatever.

Most likely he is just wanting a normal social interaction with a classmate. There is no harm in friendly small talk with a classmate.

'I don’t know how old he is, surely older . . . "

How much older do you think he is?

This could be something quite harmless - maybe you look like someone he knows. Or - he just wants to talk to you. If you think it's something more, like he's making a pass, then just don't respond to him.

What is your age? (I am assuming you are male)

Listen to your instinct and your gut feeling - if he's making you uncomfortable, try to avoid him. Going after you to the bathroom is a sign that he's not keeping boundaries. Try to avoid being alone around him, make friends with others in your class and walk out with them and away from class.

I agree about instinct and gut feelings.

I disagree. Another word for "gut feeling" is "prejudice". There are all kinds of illogical reasons why one person can be afraid of another person (race, age, ethnicity, language). Prejudice doesn't actually make you any safer.

Basic human decency in a public setting presents zero risk to the OP. If she acknowledges him as a human being she will be able to find out his intentions. Then can base her assumptions on reality rather than on "gut feelings" or prejudice.

There is no reason for her to act out of fear and prejudice. She doesn't have to spend any time with him outside of class. But a little basic human decency in a class setting where they are both students won't hurt. Being able to talk to this student (and other students) will help her feel more confident and will in fact make her safer.

Okay, and I'm prejudiced against unleashed pit bulls. Of course, many are sweet tempered, loveable pets but sometimes it's hard to tell the difference.

I do hope this isn't an inspiration for a digression into the various breeds that are lumped together as pit bulls. I know 'em when I see them and am willing to believe the OP has good judgment.

Is there a point there Roger? Because I don't see it. This guy is a human being, and a fellow student. Why shouldn't she treat him as such?

Basic human decency means saying "hello"... You seem to think that simply acknowledging a fellow human being a dangerous thing to do. I fail to see why having a simple social interaction in the context of a class is a risk. What is the danger here?

I have a nephew who has autism. He is a great, sweet, caring person (I want to still say "kid" even though he is now an adult). He has difficulty mastering the normal social interactions that we all take for granted. If you met him, you might not guess he has autism... but you would sense that something wasn't normal with him. Some people have a "gut instinct" about him that he is dangerous.

We had to fight to get him included in a normal classroom. And when he was in a normal classroom, we had to prep the classroom and deal with the prejudice from other students and parents.

If people paid attention to their "gut instinct" (i.e. fear) my nephew would have been excluded. He would have made people nervous and no one would have talked to him. It would have hurt his ability to have a normal school experience. It would have been cruel.

As it turned out, there were people who overcame their fear and interacted, even befriended my nephew. That made all the difference to my nephew and those of us who care about him.

I don't know the story of this guy, and she doesn't either. I am not suggesting that the poster needs to have dinner with him or walk down a dark alley with him.

All I am suggesting is that she give him the benefit of the doubt and treat him like a human being. Just basic courtesy is all it will take.

This presents no risk to her, and it is the right thing to do.

Geez guy. She's avoiding him, as is her right. It isn't Brown vs Topeka Board of Education.

"I opened to the door to get out of the bathroom but it opened and there he was trying to get in."

Because of this sentence, I thought the OP is a guy.

Maybe Lindt will respond.

Of course. People have every right to act on their prejudices. That doesn't make it right.

People act on "gut instincts" all the time; when they ostracize people with autism, when they follow Black people around in stores, when they complain about Middle Eastern people on airplanes. No one has answered the real question.

How are her "gut instincts" making her any safer?