How do you handle difficult job interview situations ?

Today I had a phone call with a woman to schedule an interview. She asked me a basic question about what kind of work the company I was previously employed for did. Now I had worked for one company that did Business Process Outsourcing work but was purchased by a printing company. I did my best to explain this to her but it seemed that she had trouble comprehending what I said and she got a little agitated with me and accused me of not being able to comprehend. Now I know that the interviewer pretty much holds all the cards and if they belittle you in any way, there's little to nothing that you can do or is there ? What's the best way to handle yourself when the interview is doing nothing but trying to belittle you and make you feel stupid ?

Explain that there must be an issue in the communication between the two of you, and attempt again. Apologize for the frustration. If there are still belittling comments made, you have every right to stand up for yourself. You could let her know that you feel her behavior is unprofessional. If that is a representation of the company you are applying for, look elsewhere.
An interview is not only to determine if a company wants you, but also if you want that company.

Continue looking for work... do you want to be employed by someone who is going to belittle you?

First, say something like, "I realize that this concept is confusing. It was confusing to me and I actually was present for the process! Let me try to explain it from a different angle." If that doesn't result in her calming down and even offering an apology, then I think you should seriously consider if this the type of organization that you want to be involved with. After all, the interviewer is a representative of the company and this was her opportunity to make a first impression. And I do not think any company would be pleased with a first impression that is condescending and patronizing! Keep looking!