Well I agree, it is childish, but not offensive like those other words you mentioned.
I wouldn't care if someone calls me that, I am not one of those "I die for Juve".. I love Juve, I watch them, they make me happy, sad, angry, horny, you name the rest.
I know for sure, if I will have the opportunity again just like last time, I will wake up 5 in the morning again, and try to take the train from Firenze to Milano, then Torino that 5 hour trip to watch a "shitty" match like Juve vs Atalanta. Does that make me a true fan? who cares, I do that because I love doing that, not to show off (just like I did now, what a hypocrite I am

). But seriously man, why do you care if you are called like that?