By Bonnie Stiernberg Sam Elliott has been a staple of Western-themed movies for years, but he apparently cannot abide this year’s big entry in the genre, the Oscar-nominated The Power of the Dog. In a recent appearance on Marc Maron’s WTF podcast, the actor called the film — in which Benedict Cumberbatch plays a repressed gay cowboy — a “piece of shit,” likening Cumberbatch’s character to a Chippendales dancer. “Fuck no,” Elliott responded when Maron asked whether he liked The Power of the Dog. “Why? I’ll tell you why I didn’t like it anyway. I looked at when I was down there in Texas doing 18…