he is littarly wrong because newton's 3. law states: an action creates an opposition reaction which is equal. electron guns have mass(electrons) leaving in one direction so you are pushed in the opposite one. you can use this as a rocket engine.

our technology isn't even close to there but he is wrong its possible.

and we are ignoring spinlauncher or spacelevators or even gauss guns concepts created in the last century. it is possible and he is wrong

I will give you an upvote because you are right. his post is arrogant and wrong but he isn't stupid just out of his main field which is ripping people of he is very clever at that one so no he is not dumb.