I really wish that Disney would make more of an effort to let people know that they'll be sharing a table at the Biergarten. I enjoy it, usually--I used to live in Germany so it's not big deal to me. You can have a lot of fun or it can be extremely uncomfortable--particularly when people don't realize they'll be sharing a table. We've had some great tablemates at the Biergarten but on our last trip, we got seated with a lady who was a real pill.
When she arrived at the table, she immediately turned around and told the server--we're not sitting there, people are already at this table. The server explained that guests share tables. She gave this huge sigh and as her husband came up, said loudly and sarcastically, "Well, honey, let me introduce you to the people we're dining with today." She and her family were rude to the server the whole time--a really lovely girl who I had chatted with quite a bit--her hometown was near where I used to live. A little girl was seated next to me and when she was looking at my plate, I explained what the food was and which ones my dd enjoyed. The lady whispered loudly to her daughter, "We DO NOT talk to strangers." We were all glad to get away from those people.
I'm so sorry that the OP had to observe such obnoxious behavior from her tablemate. I do feel so sorry for his wife. I also agree that an alternate table should have been found when they let the restaurant staff know that their tablemate was abusive.