The first one focuses on your opponent's effect on you. You know... the lack of ability to learn from your opposition, either by realizing the ways you're wrong or even just how and why other people think the way they do. This first focus nudges your beliefs closer to truth if you're open enough and improves your argument and understanding if you're already right.
The second one is the effect on others who are ostracized by you and those like you for their (presumably) wrong beliefs, if enough people disassociate instead of challenge them. I mean, it seems to me that pushing others with bad beliefs into their own echo chambers is only going to strengthen error, as more of their own circle merely justify their falsehoods through agreement rather than providing counter to them and planting seeds for growth.
Shame is only effective against those who give a shit about what you think, and once you're out of sight, soon you'll be out of mind.
I'm a firm believer in engaging with those who see things differently than you both for your own sake and theirs, without having to choose which side to help.
It depends a little on specifics, but... generally excommunication in what I'm describing simply thrusts them further into the circles that agree with them, and they're more likely to stay there.
Whether or not they convince others of their bad ideas? Maybe, maybe not. But they are less likely to change their own mind, for sure.