This is especially important to keep in mind because there is no way to shun a person and change their mind on the opinion that led to their shunning. Only engagement does that.
The other matter is rehabilitation. Whether he should be allowed to apologise at some point, say that he made a mistake, and be welcomed back, is something that you cannot decide for everyone. It's up to your personal beliefs, in particular your religion. Everybody needs to determine that for him- or herself, in my opinion.