Hmm, I think this is a good question. I'm at the point where I don't know how much "respect" we can reasonably expect from other people. What's normal for some is downright offensive to others. I have disrespected others and had others disrespect me, but in those cases, the offending party wasn't necessarily aware of this. This is in regards to close friends, however. Lots of people are dicks 100% of the time. Here are some of the things that people do/have done that make me feel disrespected:
I think everyone does things like this. I've had everything on this list done to me and I've done most of it to other people. I haven't met anyone who is good on all of this all the time.
As you mentioned, consistency is important, and I think that applies to character traits. Some people come off as condescending without meaning to be, but the nature of your other interactions with them and their interactions with others will give away the intent behind these slip-ups.