Weither or not it's actually being rude, those around will automatically take it as a rude laowai.  Remember you're the outsider and it's always your fault.  Though the locals can get away with always screaming to get their point across, but there are much more tactful ways to show that you're pissed and not screwing around with them anymore.

Plus if you're looking to not get taken advanage of, you get much better bargining and prices without yelling.  Yes it's a hassel, but nothing is ever quick or simple here.  But once you start yelling, they close up and become defensive and you'll never get close to the rock bottom price.

Not aggressive, but be assertive.

Stand your ground and be persistant.

Be patient and don't lose your temper.

Then you have no reason to stop until you get what you want, they have no weapons to use against you.

The moment you start yelling is consider by locals as a lost of face, and they will then clamp down and cease to "negotiate". 

There are better ways to achieve what you want without yelling or loosing your temper.  If it is a price negotiation, offer an amount and see their reaction.  If you do not get a good reply then walk away, there are many other vendors willing to barter a price.

Yesterday I wanted to buy a set of long underwear.  I saw one I liked it, and very warm, besides it fit me, but they wanted 550 Rmb for it.  I leftr, got my GF and returned with her.  She is good at this, and got them to reduce the price to 225 Rmb.  I told get to get it, she said no, they will go down more, end of cold season now.  He, he, we walked away and started looking at nearby shops.  The sales lady came after us and said 210, my GF replied 200, and the sales lady agreed.  So, I got me one hell of a wool underwear with goosedown interiors, at a very good price, without yelling at all.

I don't think that yelling will achieve all that much. Aim for firmly assertive, but with a facade of friendliness (this is much easier said than done!)

I dunno if it's the best way, but it has been known to work, besides,,,, it feels good!

Yes~why yes it is! There is only one time when you shouldn't yell and that's if the person is deaf and is hard of hearing. If they ignore you but you know they can hear you, you should shout in their ear as loud as you can! Rattle their brain a little! 

I had 2 hours to tranfer a flight in Beijing, I didn't find the train and was directed down the hall to T1, what a walk with 4 bags, by the time i cleared immigration and got to T1, i had 35 minutes and they were telling me i was too late (Hainan),i asked them to help me, then I argued with the them, then i lost it. Some Chinese guy was listening , gave me a strange look and said whats my problem, i almost decked him. I see what everybody means about keeping yr cool, but sometimes the Cheese just seem stunned. My biggest complaint is Cheese don't listen or answer is why.
After my flight took off, they sent me to T2 Air China with a ticket, i had 15 minutes (after doing the hall again) and got checked in, cleared security and still had time to wait for boarding. i don't know what Hainan Airs problem was.