If the article quoted what Slick said correctly, I don't think there is reason for complaint here. In all reality there are few restrictions, the main one being a church can not endorse any candidate.
My Pastor has studied the regulations very carefully, he will give any candidate 15 minutes to speak at the Sunday evening service, so long as the offer is open to all candidates it is ok.
Do republicans go and speak at churches? I have never seen it where I live.