Lots of people like the term "Liberal" Christianity to define anyone to the left of them, which includes a lot of true followers of Christ. I like the term Secular Christians, who are Christians in name only and deny the deity of Jesus, reject the Bible, and give aid and comfort to the enemy (moral relativism). Secular Christians are the followers of a dying church while all the rest are growing, both Protestant and Catholic.
"Moreover, evangelical Christianity is the most rapidly growing faith in the United States"
If you actually read the entire article, you will see that the percentage of Evangelicals in the US population has remained constant, at a steady at 25% for decades. What has changed is the social class, with Evangelicals moving into the more highly educated and highly paid elite schools and professions. The links in the article have demographic statistics.