From John Wesley’s sermon “On the Wedding Garment“:
When things of an indifferent nature are represented as necessary to salvation, it is a folly of the same kind, though not of the same magnitude. Indeed, it is not a little sin to represent trifles as necessary to salvation; such as going of pilgrimages, or anything that is not expressly enjoined in the Holy Scripture. Among these we may undoubtedly rank orthodoxy, or right opinions. We know, indeed, that wrong opinions in religion naturally lead to wrong tempers, or wrong practices; and that, consequently, it is our bounden duty to pray that we may have a right judgment in all things. But still a man may judge as accurately as the devil, and yet be as wicked as he.
Right opinions about every doctrine are no guarantee of holiness. Does Wesley say that orthodoxy is a trifle?
The real danger of bad doctrine is bad practice.