This is dangerous because it is not the true gospel of salvation by grace through faith, new believers are not yet equipped to discern when presented false gospel.
it is easy for them to draw back to works to attain righteousness and feel condemned when they fail.
It is also dangerous since they can spread this faulty not even gospel to others.
This affect Christians to day in a way that they try to keep laws to please God, they end up condemned and fearful.