Hi A.,
My advise would be to ignore the tantrums and in no way give in to what he wants unless he asks in a plesant voice with please and thank yous'. You need to nip this in the bud now or it will only get worse. Explain to him that you dont speak to him in that way and you dont expect him to do the same. "He needs to talk to Mommy the nice way Mommy talks to him or you wont talk to him until he stops whining at you." As far as the bath, did he see something on tv or have a bad experience with water in some way? maybe choked on it in the tub while rinsing hair, etc? Try and see why all of a sudden he is upset. If nothing serious, make a game out of it. Someone else had suggested to another Mom with the same problem to get bath crayons and show him you are coloring on the tub than making it clean, than try on his feet than belly, etc...till he is clean....i always had lots of toys in the tub for him to play with while i washed him, that way he had no idea what i was doing because he was too distracted. Make bath time fun. Let them pick out the toys they want to play with and the kind of smelly bubbles they want, that way its all their tubby!!
Good Luck