I agree with ElizabethN. I might ask, how would you feel if someone else asked you for help and then did this to you?
I'll add that we don't tolerate this kind of behavior in our house. We tell our kids that this kind of thing is very disrespectful to others, and that it reflects very poorly on the person behaving badly (e.g., people might not want to play with you or be near you at all, and other kids might even say mean things about you because they feel so frustrated). A tantrum in a situation like this would earn a punishment of some sort in our house (often a loss of a privilege).
I see taking instruction gracefully as a critical social skill: learn this or have big trouble when you get older.
Kids naturally test their limits, which is normal. Part of this process involves figuring out which behaviors are acceptable and which ones aren't. I see part of my job as a parent as being teaching them which ones are which. IMO, tantrums are never okay, not even in a toddler (expected and age appropriate =/= okay).
