Online Social Networks have been adopted by political groups in order to improve the reachability of protest movements. As such, these networks give us a rich data source for estimating the impact and participation on these events. In some situations, though, the organizers employ the use of bots to inflate the real impact of the event. These bots promote ideas while being disconnected from the political group social network. In this paper we investigate the dynamics of message sharing on the Twitter network during two contrastive protests that took place in Brazil in March of 2015. During the data collection, it was observed that some of the messages were massively shared by bots. The dynamics of message sharing, with and without the use of bots, were contrasted by means of different methodologies from the network science literature. It is observed that the use of bots indeed impacted on the network metrics, thus making it easier to detect such cases.