Moderation isn’t about filtering away the opinions you don’t like. That drives people away. Moderation is ensuring everyone who has an opinion contributes it.
To contribute an opinion is to make an investment in the community.
The second a member says “I think…” or “I believe…” you can be certain they will return to your community again. You can be certain they will develop a relationship, positive or negative, with the people that reply to their opinion.
You can help by sending messages to people with similar opinions, or conflicting opinions. Invite them to contribute their views. It takes very little work to start intelligent discussions.