This paper examines the reasons behind people’s decision to participate in the pro-Park rallies against the impeachment of the former Korean President Park as well as an explosive growth in their participation numbers by focusing on the view of these rallies as the silver generation’s counter-movement characterized by an unconventional, short-term collective contentiousness. The empirical findings of this study are based on the field survey data collected from these rallies’ participants and the in-depth interviews with the participants in order to obtain more insights into the nature of counter-movement rallies in the information age. The results of our analysis imply that the decision to participate in the pro-Park rallies was not driven by collective mobilization as it had been in the past, rather being a result of voluntary mobilization caused by the individuals’ confirmation bias in response to the anger targeted at the pro-impeachment rallies. We find that this group of protesters attached rather high a value to their own political efficacy through participation in such rallies, which is a phenomenon that appears to be stronger among older citizens.