Why do some christians tell others what god isnt as opposed to what god is?

i am still finding absurd and insulting ones intelligence when some tell me or others "gods not a genie" of "god isnt santa cluase" i was also told "god is not my bellhop" - really want to know when did this start - i was raised in chrisitan home , church and christian school - i didnt hear gods not a genie thing til i was in my 30s - is it me or this a big no duh!!!!! what or who makes some people think others think of god as genie or santa clause etc, whats with this breaking news to use we already know - is it me or is this just unecessary and kind of stupid and well no smart and again no duh!!! i never ever thought as god as being anything other than god - never thought he was a genie but felt acused and insulted by this - if one is going to witness or be a witness - tell someone what god is not what god isnt? hello logic then again that is too much to ask of some lol