Isn't this obvious? These are negative experiences caused by their Christian programming. Have you ever wondered why people who aren't aware of Christianity and haven't been raised Christians have never reported any problems with yoga, meditations, Satanism or anything that Christianity says is bad? Why religions like Santeria and cultures like Africans and Native Americans that practice witchcraft or Shamanism never report any attacks and convert to Christianity as a result of them? Very simple, it's because they have no subconscious guilt or fear of what they are doing instilled to them by Christianity.
These people most of the time aren't really attacked by beings, but the attack and negative hallucinations are caused by their own subconscious guilt and fear. In some cases it could be enemy beings, as what Christians think are "demons" are enemy angels and greys, the beings behind their own religion and by giving into them they just take their bait and do what they wanted in the first place.
That's why the JoS site says it's important to deprogram yourself fully from Christianity and completely remove any traces of it from your mind before doing any advanced occult/spiritual things, as they may cause negative experiences.
It also says that nobody can advance safely into the occult without Satan's protection (by doing the Dedication Ritual first), as there are enemy beings (the same beings who are behind the hoax of Christianity) that will try to stop and prevent humans from acquiring any serious power by scaring them into returning to Christianity.
If you know someone who has negative experiences or enemy attacks while doing yoga or meditation, tell them to not panic and ignore them, as it's either their subconscious programming or enemy beings trying to stop them, and if they simply ignore the attacks they'll eventually stop. The best way to stop an enemy attack is simply tell the enemy beings "f*** you" and continue doing what you were doing.
I have seen many people here who had attacks from enemy beings and they just ignored them and kept doing spiritual things and they just stopped, as the enemy knows they can't stop them and they just give up.
I have also seen people who got either subconscious negativity or enemy attacks or even pressure from their friends and family and they gave in and went back to Christianity and later regretted that because they realized it's foolish so they begged Satan to take them back. This happens all the time if you read past posts.