I used to let people get away with disrespecting me. I found that while I personally didn't feel bad about it, this ultra-passive behavior also lowered my esteem in the eyes of others as well. And I think it hurt my chances in getting raises at work and getting a few women I was interested in. If I don't stand up for myself in the face of disrespect, other people shouldn't trust that I will stand up for them either, right?
I recently started a new trick. I give people a compliment first before I bring up my valid complaint about their behavior. Here's a recent example with a secretary at work, with the Vice Chairman of the school board present, verbatim:
"I consider you a fair and honest person. So I'm sure you understand that I mean no offense when I ask you to please not interrupt me when I'm in the middle of a conversation."
It worked. Due to my giving her a stellar reputation to live up to, she had no choice but to immediately and emphatically apologize. I think I earned her respect as well as a feather in my cap from the big boss.