Why do some guys tell girls to shut up in a joking way?

[iamminzy]

I mean you say something and they tell you to shut up or f you... Is it it guys nature to tease girls like that? Should i take it serious or just in a joking way? They seem to say that just in a teasing and keeps calling me man dude wuts up bro, like im a guy.... its getting a little annoying... shall i play along with him? lol

[sarahprincess]

I wouldnt go along with it, its degrading, even if its supposedly joking, because one day it wont be.

[steviej]

Maybe you just need to stfu!

[Ugly_Idiot]

Sounds like a typical annoying male (i can be similar )

Just give him it back, it's just banter. Take the piss out of him!

And if it's getting to you then you need to tell him and show your serious.

[iamminzy]

Uh steviej that's wasn't nice I did my even talk alot n just cuz u guys thinks that girls talk alot doesn't mean that all girls are like that get a grip of yourself man

All I did was joke around but he said shut up and it's kind of annoying in a way n imagine if a girl kept saying shut up to u it eventuay gets old

[Yet another guy]

From urban dictionary:

3. shut up
Expression of incredulity. Similar to "no way" or "Wow, I can't ****ing belive it"
What? My lazy ex got a job? Shut up!

I'm pretty sure it isn't a guy specific expression.
Impossible to say out of context though. If you were debating, it could mean that he's giving up the argument.
Or maybe you really were talking way too much and he meant it literally.

Why do guys like to tease like that? Because many girls respond well to teasing. Furthermore, I know that I wouldn't want to be around someone who took lighthearted joking as a personal insult. So I guess it means that he has the impression that you aren't hypersensitive or insecure.