I hear you.
Most of the world's religions were founded by other men--on the same 'level' as you and me (as far as authority is concerned). Christianity is unique in that its 'Author' is our Creator, which means he "gets to say" what is true. (Like an author gets to say what his book 'means'.)
And the thing about truth is that there are not 'many truths,' there is only one 'True Truth' (as Schaeffer used to call it). Jesus came and told us the (one) truth, and said 'now, go tell everyone else what I've told you,' and so we do--it's news, coming from a source 'above us' (on a higher plane of authority), and people will either hear it or they will not. That part's not up to me, though I do hope people will hear. The guy who delivers my mail isn't 'special' just because the letter he bears has great news inside. I'm thankful to him for delivering me this great news, but the one I'm really thankful for is the one who sent the letter in the first place--if that makes any sense. The mailcarrier doesn't give me the news on his own authority--the message itself is stamped with the authority of the sender.
It's also true that the message may offend some. Again, not what I would want, but that's also not my responsibility. Maybe 'how' I share the news is within my control--thing like demeanor and accuracy--and we try, with varying degrees of success, to be 'gentle in manner, but powerful in substance'--but the essential content of the news is not mine to tweak or revise. (Think if the mailman 'edited' a message from your bank or from the mayor...that's rather out of line, right?)
It's also OK if we don't agree on this. I believe this conversation, in most cases, is firmly within the realm of persuasion and civility. Make sense?