AT&T's recent deplatforming of Newsmax, one of America's most influential cable news channels, should alarm everyone, including liberals. We are all at risk when censorship occurs—when one is silenced based on his or her point of view. The facts strongly suggest that partisan and ideological motives played a sizable role in AT&T and DirecTV's decision to remove Newsmax on January 24, when some 13 million homes were deprived of the channel—including my own. After the recent State of the Union address, I turned to Newsmax for their coverage, but was surprised to find it suddenly missing from my channel guide....