Speaking from the perspective of a person with ASD / Asperger Syndrome who has major sensory impairments.
I can say that the person's who you are talking about's behaviour could be caused by his ASD and sensory impairment.
Shopping in a big shop can be a complete nightmare for people with ASD and sensory impairment.
Hypersensitivity to sound, movement, lights can cause a person with ASD who is hyper sensory to go into the fight, flight and freeze response.
If this happened to the man who you are describing, then it perhaps is understandable with regards to his behaviour, even his rudeness, as during the fight, flight and freeze response, the primitive primate mind takes over and makes the body do what it needs to do in order to escape what is perceived as danger.
I understand from your perspective Summer_Twilight that his response may not be what you like, and sure, you have the right to choose who you want to be in a relationship with, and if his behaviour is something that you don't like or can't adjust to, then sure, you have the right to not befriend / or engage in a relationship with this person. Fair enough.
Perhaps he would be better in a different environment. one that isn't so busy in terms of sensory information.
Perhaps you should tell him next time he is on a date and being judged.
Perhaps you can value the speed of his shopping, as sounds like he was efficient.
As for long greasy hair, this is more to do with his own personal hygiene and there isn't really a good excuse to explain this behaviour apart from poor mental health. A long time ago i had long hair, down past my shoulders (now my hair is shaven into a crew cut), but even during this period when my hair was long, i showered every day and washed my hair frequently. Although i have to admit, having long hair can be a bit of a burden if your not the type of man who wants to spend a lot of time looking after your appearance.
This is one reason why i cut my hair short, so that i no longer had to spend an hour getting ready before leaving the house. After that, it takes me 10 mins in the shower, put my clothes on and gone, all done in 20 minutes and still looking presentable, clean.
I don't know about the geek girl thing. I personally find all attractive woman attractive regardless as to what their into.
I see what is there. Geek girls, Rock Girls, gamer girls, sport girls etc. What there into is just a facet of their personal interests and doesn't detract from their beauty.