"should(n't) be [v-ing]" vs "should(n't) [verb]"
They seem to be the same to me.... however, is there any reason why "should(n't) be v-ing" is preferred by many native speakers? What's the subtle difference between them to both the talker and the listeners?

Thanks!

Added: Thanks for all your answers! Just I'm still a bit confused.

I saw something like "You shouldn't be talking to me like that!" and was wondering whether it would do by saying "You shouldn't talk to me like that!" in this case. Is using the former one suggests that in some times/situations one is allowed to speak the way s/he "is"?

Take Kenneth's example: "You shouldn't be running with scissors." Is it suggesting that sometimes you CAN be running (or can run?) with scissors, or is it more like a habit to emphasis "now" in English?

Question

"should(n't) be [v-ing]" vs "should(n't) [verb]"
They seem to be the same to me.... however, is there any reason why "should(n't) be v-ing" is preferred by many native speakers? What's the subtle difference between them to both the talker and the listeners?

Thanks!

Added: Thanks for all your answers! Just I'm still a bit confused.

I saw something like "You shouldn't be talking to me like that!" and was wondering whether it would do by saying "You shouldn't talk to me like that!" in this case. Is using the former one suggests that in some times/situations one is allowed to speak the way s/he "is"?

Take Kenneth's example: "You shouldn't be running with scissors." Is it suggesting that sometimes you CAN be running (or can run?) with scissors, or is it more like a habit to emphasis "now" in English?

Answer

It isn't a case of preference - it's a case of choosing the right verb form for the context.

The difference is the same as between the present simple ( to refer to a general fact or repeated activity) and the present continuous ( to refer to the action taking place at the moment).

For example:

"You shouldn't smoke"  
=  This is a general fact - it's bad for your health

"You shouldn't be smoking"  
=  You're smoking at the moment, even though you shouldn't ( perhaps you're in a place where it's prohibited).

Answer

Hi SJ Jhuang,

Let's take this example: the machine should be working. It means that the machine should currently be working because you pushed the on-button two minutes ago.

If you say 'the machine should work', then you could mean that you expect it to work because a team repaired the broken machine some days ago.

I hope this examples help,

Kind regards 
Karen

Answer

It's all about meaning, they are different things.

You shouldn't be running with scissors (you are running now and I'm telling you that you should not)

You shouldn't run with scissors(just telling you in general not to do this action)

In this example both would probably work in context cause this is something you should not do period.

However think about this
"You shouldn't be talking" . You are talking now and I'm telling you that you should not be.
To say "you shouldn't talk" is weird cause of course you should talk when it's appropriate.
However if someone says "you shouldn't talk" they could be trying to be funny or really mean. It's just a matter of context.

Answer

One difference is that “should(n’t) be [v-ing] is often used for to make a statement about what should or should not be done RIGHT NOW, but “should(n’t) [verb] is used to make a statement about what should or shouldn’t be done EVER.  Example:  You shouldn’t be smoking = Now is the wrong time or place to smoke vs. You shouldn’t smoke = You should never smoke.

Answer

be -ing