Flying does not contradict gravity. Anything that flies does so temporarily, as long as there is active force involved to counter gravity.
Equal acceleration is observed in vacuum. I doubt that it was known to anyone in the Midle Ages. They would surely think a rock would fall faster than a feather -- and that is true as long as the effects of air resistance are present.
A medieval man would have no problems accepting gravity. He knew just as we do that jumping off a great height is not a good idea. He accepted God on authority of the Church.
I think your point was that believing in God is hard and believing in gravity is easy. I point out that observation of flying and falling objects does not support gravity as we know it to operate, but observation of the Creation confirms our faith in God every time we open our eyes. The reason you look at falling or flying objects and wisper "gravity" is because of the school indoctrination. You should be wispering, "God".