Many atheists started out as believers through the usual mechanisms of indoctrination, but became atheists when reason kicked in and they started thinking "this shit makes no sense at all, and there's not one damn thing that can only be explained by having a god"

while I have the greatest respect for Swift, I never did get that quote.

However in general, speaking up, having the discussion where perhaps previously no discussion was being had, can persuade those who didn't know there were alternatives to Official Wisdom, to start thinking that there are.

actually get someone to see that something is unreasonable.

Evidence and logic and respecting human dignity can cause changes in understanding, behaviors and, perhaps, even beliefs.