Seriously its a word and is in the dictionary so why could I not have the word?!?!?!

It is in some dictionaries, and not in others. What matters is that it is not in the ENABLE word list, which is used for this game.

I didn't find “poo” in any dictionary (I haven't tried all), only “poo-poo”.

BTW at other words (i.e. blanco, negro) there are differencies in online Hasbro Scrabble dictionaries for US&Canada and for rest of the World (Europe&Asia&Africa&cetera).