It may not make a difference to you, but if I paid $30 for a specific seat, I would expect that seat unless there was an actual reason beyond people wanting to sit together. They could have paid for seat selection themselves. Now, if I were asked instead of told to swap seats, I would strongly consider it. However, there should be no expectation that I move, and declining to move would not make me "a baby." I think adults can stand to not sit next to one another for a single flight.