Hell just emphasizes your answer or reaction. It's only not polite if you say "hell no" but only in certain cases. Saying "hell yeah" is perfectly fine when speaking to friends but not in any formal situation. Example of a rude "hell no" and a acceptable "hell no" John: Do you want to go on a date with me? Sue: Hell no! (that's rude) John: Do you harm puppies? Sue: Hell no! (that's not rude)

The word "hell" is a mild expletive to show strong feeling. It is not particularly polite.

Infernally positive!! :D