Cindi,
First of all, you seem to be a very intelligent, caring individual.  I applaud your expedition into the Deaf World. My comments below may seem sharp, but are meant to be so only in the sense that a surgeons scalpel is intended to be sharp. The surgeon himself has no desire to cause pain to the patient, but rather to deal with the underlying issue in an efficient, effective manner.
Here are my thoughts on the topic:
You use loaded words like "intolerance, shunned, and prejudice" to refer to Deaf behavior.
You then use mitigating words like "differences" to refer to Hearing behavior.
Deaf people prefer to be with other Deaf people for many reasons, the chief among them being the ability to communicate at high speeds.
Imagine yourself in a sports car on a multi-lane highway.  Now imagine it is a 75 mph zone but in every lane, driving side by side, there are slow-pokes doing 30 miles per hour.  How would you feel after just a few moments of having to drive behind these people?  Now imagine having to commute to work everyday there and back behind these slow pokes?  Now imagine they are doing 15 mph instead of 30.  Now imagine they frequently break down and ask you to tow them to their destination.
All you want to do is get to work and get home and you'd like to do it at full highway speeds.  Can you imagine the frustration?
Now, imagine one of the lanes frees up and starts moving at 75 miles per hour.  Would you hang around behind the slowpoke, or would you hastily move away from the slowpoke and get into the fast lane?  It isn't that you have anything against the slowpoke.  You don't really know him.  You just want to get to where you are going and getting in the fast lane is the least frustrating, most enjoyable way of getting to your destination.
It is the same for Deaf people every day of their lives.  They are surrounded by Hearing people and their slow-poke signing.  Sure, we tend to avoid you, but not because we hate you.  We avoid you in the same way you get out from behind the slowpoke on the highway. It is nothing personal.
Another example is a bee or wasp.  How do you react around wasps?   You tend to avoid them because they can (and sometimes do) sting you.  If you are sitting at the kitchen table near a closed window and a wasp comes up to the window and buzzes against the glass how do you react?  You get uncomfortable don't you?  You feel uncomfortable even though the window is closed and it is totally irrational to think the wasp could break the window and sting you.
It is the same for many Deaf people.  We have been stung by hearing con-artists, mechanics, contractors, and medical professionals. And maybe not us personally, but we know of others who have been stung.  And just the fear of getting stung is enough to cause us Deaf people to behave the way we do around Hearing people.
I need to state this very clearly:  It is absurdly easier for a Hearing person to learn to sign than it is for a Deaf person to learn to talk.
This fact seems lost on many Hearing people.  They expect us to accommodate them.  That is like expecting "Interstate Highway 5" to slow down to accommodate bicycles.  That is absurd.  If you want to get on the highway you should speed up...not the other way around.  If you are incapable of driving at highway speeds, content yourself to driving around town at 30mph (attending deaf events and sitting on the edges doing more watching than signing). I have a bike.  I often bike to work.  I don't label motorists as prejudicial and resistant to accommodating me when they speed past at much higher speeds.  I realize my place on the road and I enjoy the ride for the exercise.
If I want to be accepted on the road I have to invest in a faster vehicle.  If Hearing people want to be accepted in the Deaf Community they need to invest in ASL classes, videos, lurking time, and tutors.
Consider how medical doctors feel when they go to a party or to church.  Everyone and their dog comes up to them and starts listing off symptoms for some free medical advice. So what do doctors do?  They get unlisted phone numbers. 
Do you label doctors as prejudiced because they say, "Let's schedule you an appointment at the office so I can run a few tests" (instead of helping you right there at the party).  They don't want to waste their party time on you.  They want to go chat with their friends and have a good time. Do you label them as impatient because they don't want to talk to you in that circumstance and want to be paid for their knowledge?
If you want a Deaf person to be patient with your slow signing, you could simply PAY one of us to be patient with you. (That works really well, heh.)  Hire a tutor.
Okay, now on to a separate topic:  You state that handing a deaf person a piece of paper to write something down is a "no-no."  Who told you that? I don't think there is anything wrong in general with handing a Deaf person a piece of paper and pencil.
While it is likely the Deaf person "stomped off" in frustration, it is also possible that there are other reasons. Maybe she couldn't write very well or at least couldn't write the particular concept she had in mind and was thus embarrassed?
The Deaf person approached you, not the other way around. You were innocently trying to communicate via a time-tested approach.
Cordially,
Dr. Bill