Old people can be....... a wealth of knowledge, wonderful to be around, and a source of inspiration.
People can be mean, rude, nasty, old or not.
Basically what Morgbug said...

Here are two examples:
Saturday afternoon, I am the local McD's. Took the kids there while waiting for Nadine to get her hair done. Place is packed, and I finally find a seat, buts its only a table for two. I walk over and notice a man sitting at a table for 4 all by himself.
I start to sit the kids down, but realize this isn't going to work, and I nicely ask if it would be OK for us to trade tables so I can sit with my kids.
"No... I was here first, tough luck for you"
"I understand sir, but since you are all alone and I have these two little kids to take care of, it would be a great help if we could trade"
"No" quite smugly he says.
Another time and place I would have been dragging this man out of his chair by the neck, but I have worked out a lot of anger issues since then...

So I proceeded to help my kids the best I could until someone else came up and offtered the table they were leaving.
Now, this man was "older" he smelled, and looked like he wore the same clothes everyday. I guess I knew in my heart when I first saw him he wouldn't move, but reminded myself not to be close minded and judge others by their appearance... didn't work this time.
Another story... I spent a great deal of time with a lady helping her with some technical issues (I work support for a wireless company) she was qite elderly and for some reasons her son set her up with wireless internet services. These can be very complex to troubleshoot, and looking in her file she had numerous calls for help, but at the beginning most of these her son would call in. I spent some time helping her, got it all sorted out, she thanked me and asked how she could call me back if there was trouble again. I gave her my first name, and tech ID, with some trepidation as I really can't be her personal helper each time she can't figure out how to open an e-mail...
A few weeks later I get a package addressed to Scott ID 4069 care of the company I work for. When I open it up there was a gift certificate for a local restaurant, and a nice letter from her. The letter basically thanked me for all the help, and she was sorry to be a bother. It went on to say that she usually asked her son for help but he recently was killed in a motorcycle crash. She said talking to me reminded her of him.
I keep the letter at my desk as a reminder that sometimes there is a another story you don't know about.
Scott