Tech giants like Google and Facebook always deny that their platforms favor some viewpoints over others, but then they don’t do much to avoid looking censorious. . . . Dennis Prager’s “PragerU” puts out free short videos on subjects “important to understanding American values” — ranging from the high cost of higher education to the motivations of Islamic State. The channel has more than 130 million views. . . . As you might guess, the mini-seminars do not include violence or sexual content. But more than 15 videos are “restricted” on YouTube. . . . This means the clips don’t show up for those who have turned on filtering — say, a parent shielding their children from explicit videos. A YouTube spokesperson told us that the setting is optional and “based on algorithms that look at a number of factors, including community flagging on videos.” . . . PragerU started a petition calling for YouTube to remove the restriction, and more than 66,000 people have signed.