I'm had my mind changed on a number of issues, large and small. Usually not immediately, with one single argument, but it does happen. And I've seen it happen with plenty of other people as well.
There's lots of evidence that people do change their minds. All sorts of famous figures who say one thing when they're young and then, when they're older, talk about how they feel differently. It's actually not that uncommon for thoughtful people willing to examine new evidence or consider new arguments.