Tell me. What separates your mythology from the over 3000 other systems of mythology on this planet? What is it that sets your religion apart from all others that it should be believed?
What's offensive is telling other adults because a fairy tale youve been sold through the geography of your birth should dictate what they can and cannot do. Worse yet, telling the same to children who don't yet know or understand how to defend themselves from this psychic bullshit.
No atheist claims to know anything other than the existing arguments for the existence of the Christian God and associate mythology are about as solid as those for Ahira Mazda, Zeus, Odin, Maui and Pele, the Buddha, or any of the various animal spirits.
Pull the religion out from over your eyes and see it for what it is - a con.