Let's say I enjoy walking in the woods while pondering the meaning of life, and somebody tells me that I shouldn't because "That's what witches do". Should I stop? No. Witchcraft has no power over me, and changing my life around it would give witchcraft power where it has no right to be. I'm not going to call myself a witch, because I'm not one, but walking around in the woods while pondering the meaning of life is perfectly acceptable.
Although I find the idea of Christian Yoga to be a little odd, and don't practice it myself, I disagree with the notion that Christians who do so are worshiping pagan gods or anything of the sort. Yoga poses, and symbols like the pentagram, have no meaning to us as individuals other than the meanings that we assign to them. Not to mention that things like exercise, stretching, standing in particular poses, or whatever existed long before Yoga was a thing. Maybe call it something more descriptive and less potentially misleading.
This one is interesting, in part because the pentagram wasn't associated with Satanism until recently (the mid 20th century, if I'm not mistaken). It was long used in Christian culture, to symbolize the wounds of Christ and represent the star of Bethlehem. Pointing up or pointing down, the orientation didn't seem to matter. The pentagram, in various rotations, can be found in medieval Christian literature and on the walls of old church buildings. It also existed long before, representing various things through the years. Some people choose go assign it an occult meaning, but there's nothing inherently occult or unchristian about it.