Not going to go into it, but you are deliberately taking what they are saying and twisting it around. Nobody is doubting that we could not exist without gravity. Quot changing the subject. By the way, I'm taking a poll of thousands of people around the world, and I want your opinion on something unrelated... How old is the earth?
In that case then gravity is observed on a daily basis. Gravity is a fact of life and it is undeniable. Not so for evolution which has never been observed. Your friends are trying to foment skepticism and imply that there is nothing scientifically true. There are many things which are indeed scientifically true and are observed to be true all the time. Evolution, the transformaton of one species into another by totally materialistic means, has never been observed. It is therefore pseudo-science, not science.