Focus on the people that are doing what you want them to do.
Don’t tell them what to do, don’t tell others what not to do. Just shine the spotlight on people what they should be doing – ignore the rest.
If you want members to talk more about any issue, focus on the people that are talking about it. Write news posts mentioning the names of these people, create a forum for these people and give these people op-ed columns.
If nobody is doing what you want, that should be a good sign that you want the wrong thing.