I'm differentiating harmless banter as something like poking fun of differences of men and women. If it starts to go sexual then it depends what the conversation actually is. If the topic is more along the lines of simply having sex or who you had sex with or even details about that sex, that isn't exactly sexist. That can be harmless conversation. I think what the original poster was talking about though (and what I've been posting about) is more abusive and sexist comments or those alluding to physical violence. I don't think it's ever "harmless" to talk about beating your wife. That is not a joke to me.
Words are not always harmless. Some things you can shake off, some are abusive. How would you feel if, in your circle of friends, ftm transsexuals (assuming they thought you were just a regular bio male) were brought up and one of those friends said something like, "You got a c--t for a reason, you're not a man and I'd f--k that idea right out of your head you dumb bitch!" and then laughed? Would those be harmless words then? I've heard someone say just about that and I didn't consider it harmless or funny at all.
The problem I have with some of the banter is that it can easily move from a harmless phrase (someone says, "Oh yeah, I'd do her" - pretty harmless) to something else really quickly ("Yeah, I'd put her on her knees where she belongs!" - sexist).
As @kyril said, the harmless stuff is usually easy to distinguish. But I still feel the types of things the original poster was talking about (physical violence) is not that type.
I've heard it all and I've experienced a great deal of it myself and I just see too many ways talk like this is not a good thing and it shows lack of respect.
