Bill Maher addresses silly claims by a variety of prominent conservatives that Christians are heavily persecuted and Christianity on the verge of being criminalized. Funny but also pretty accurate:
So why is it that some Christians really do feel victimized? I think it's worth leaving Maher's (admittedly funny) ridicule aside for a moment and seriously asking why.
Mainly, I think, it's because a lot of older Americans, especially we Baby Boomers, grew up at a time when Christianity was the de facto established religion of the U.S. (in disregard of the First Amendment). For decades public school children recited government-approved, often clearly Christian prayers. (Jews were free to leave the room.) The Pledge of Allegiance was mangled in 1954 to insert "under God" after "nation," converting the original "one nation indivisible" into the rather incoherent "one nation under God, indivisible" -- making it sound, presumably unintentionally, like an attack on the idea of the Trinity. "In God We Trust" was similarly added to currency in 1957, in defiance not just of the Establishment Clause but the sentiments of deeply religious persons who oppose such casual association of God's name with mammon, including many devout Jews going back at least as far as Jesus of Nazareth, famed for driving the money changers out of the Temple and advocating separation of Church and State (see Matthew 22:15-22, and Mark 12:13-17, and Luke 20:20-26).
Things have changed a bit. The country remains majority Christian but less overwhelmingly so. There has never been an expressly non-Christian president and there are very few non-Christians in Congress. (The Supreme Court, interestingly enough, is 2/3 Catholic and 1/3 Jewish. The previously dominant Protestants are no longer found on the Court, something that would have shocked the many Americans who voted against JFK in 1960 because he was Catholic.)
(Update 2015 June 18: I originally wrote that "there has never been a non-Christian president," but there is at least one clear exception: Thomas Jefferson, who in private correspondence made it clear that he was a Deist who greatly admired the teachings of Jesus but rejected Christianity. Other presidents may have been private Deists as well. Washington, for example, was nominally an Episcopalian but reportedly never took Communion or knelt in prayer, and his public religious statements were consistent with Deism. Lincoln similarly referred to God and Providence, but he did not belong to a church and several of his close acquaintances said that he had no religious faith.)
belonged to no church and his speeches sometimes referred to God or Providence but not to Christ, and several of his friends said he had no religion.)
And most recently, of course, same-sex couples have been allowed to marry, a real shock to religious conservatives.
Since some states and localities include sexual orientation in their laws against discrimination in commerce, a tiny handful of businesses (bakeries, florists, and commercial wedding venues) have wound up being sued for refusing to do business with same-sex couples. Meanwhile, other businesses with religious owners have had to tolerate contraceptive coverage in their health insurance. Churches and other religious institutions are exempt, though the new rules do apply to profit and non-profit concerns that happen to be owned by religious persons or organizations. This is basically the same rule that applies in employment discrimination. A church can require all its employees to be members of the faith, for example, but a hospital owned by the church can't put the same restriction on its doctors or janitors. (The Hobby Lobby decision was intended to require private businesses not publicly traded to be treated like church-owned hospitals, though its practical effect may be broader. Either way, the beliefs of religious business owners apparently count for more than those of mere workers.)
In brief, to many conservative Christians were accustomed to having their values given the force of law, these social changes have come as a shock, and to some their loss of power apparently seems like oppression.
In L Sprague de Camp's 1941 novel Lest Darkness Fall, an American archaeologist visiting Rome finds himself transported by a lightning flash from the 20th century to the 6th. In one scene he encounters an angry Roman who complains of religious persecution under the tyranny of the Ostrogoth emperor. The archaeologist is puzzled, since he had the impression that the Roman government of the time favored freedom of religion. It turns out that the angry Roman feels persecuted because his sect is no longer allowed to persecute other sects. When I first read that I thought it funny but implausible. It appears it's plausible after all.