I believe I have a solution. I do not consider myself a conservative, but I do enjoy coming here to get another perspective on issues. My solution is twofold: 1. Make the sub approved submitter only; 2. Set AutoModerator to automatically remove any posts from people not on the approved submitter list. Item 1 you should already know how to do. If you are not familiar with AutoModerator, allow me to assist you here. If it is not already configured, go to https://www.reddit.com/r/conservative/wiki/config/automoderator and click create page. Then add this code (I've even written it specifically for this case):

type: comment
~author: is_contributor
comment: |
    This subreddit is submitter-only. Your comment has been automatically removed. Please apply to for approval here: https://www.reddit.com/r/ConservativeRequest/comments/4cref1/please_complete_this_simple_questionnaire_in/
action: remove

Using this code with AutoModerator and approved submitter only mode will ensure that only those who you (the moderators) have approved can post or comment here. This solution locks down posting and commenting to only those who you approve, and removes comments from everyone else. This, I believe, is the best solution for everyone if you wish to eliminate non-conservative posts. I hope that you will reconsider your decision using this method. This subreddit should remain a source of other perspectives for those who wish to expand their sources on an issue.

A personal note: I am, in principle, opposed to the idea of restricting contributors in both posting and commenting. Such a policy creates a safe space-type hivemind environment that fails to provide any meaningful dialogue. If this is the goal of the subreddit in the eyes of the moderators, so be it; I'm nobody to try to stop you. However, I think I can help find a better middle-ground than going fully private with this method.