There is actual evidence that circumcision was practiced by some in pre-civilized times, such as in cave paintings and ancient Egyptian paintings. It follows that God din't need to invent this custom, but imposed something that was out there. Better not be offended by historical facts, but use thought to come up with squaring the facts with your beliefs. For example: Come up with a reason why circumcision is good for the child and give credit to God for knowing it.
Western-backed Syrian rebels say kill foreign Islamic State (Reuters)
from the article: Actor Russell Crowe apologizes for anti-circumcision Twitter rant