LAUGHING SO HARD...
Check out this article from News-Leader:
Assemblies of God pastor says yoga has 'demonic roots.' Yogis respond: That's 'ludicrous.'
I was stationed with a religious zealot, who felt compelled to warn me that yoga was one of the many paths to the devil. I laughed at him and asked if it was just yoga or all forms of exercise, because that was how I used it. He said it led to lifestyle changes, which did nothing to staunch my laughter, as I'd heard similar stories, but they were positive and advocated for improved diet and healthier habits, none of which I'd ever heard associated with Christianity.
I remember learning to meditate and telling people how excited I was to have this wonderful form of stress relief...I was told that I was letting the devil in the door and to not come near them in case I could release him out to them...wtf? Yeah, I was 25 and so confused...I left them and stayed with meditation...it is absolutely ludicrous...
This is pretty common (if generally more low-key) throughout the evangelical world. Yoga, Halloween, sometimes traditional Chinese medicine, rock music, anything a little different or fun, is said to originate in or promote or condone covert Satanic activity.
Sometimes even as a Christian I used to wonder whether some of my fellow believers were more impressed with Satan than with god, as they certainly seemed to fear Satan more.
In its extreme form, the notion that one can, by "sinning", empower Satan to interfere with the work of God in our lives, ends up being a fulcrum of control. If you think demons will infiltrate your soul if you have a lustful thought or skip Bible study then you'll be desperate for prayer or even outright exorcism. There's a church in NW Indiana named Hegwich Baptist that believes demons can possess Christians and that ministers to its adherents primarily through exorcisms. It can get really nutso.
Mostly though it's just a low-grade suspicion of unapproved amusements or disciplines and claiming you "might" be "opening yourself up" to or "giving place to" the devil as a way to warn people off. At some level people know that when things go wrong in their life it'll just get blamed on that yoga class or acupuncture treatment, so they figure maybe it's best to not even do those things. It's a way for church leadership to create a spiritual ghetto to confine their people to, so they are dependent on them, and only them, for advice and help.