Gandalf different approach towards magic rings in Hobbit Movie 3 and LotR Movie 1

My concern is only about the movies:

In Hobbit 3 at the end of the movie Gandalf says that he knows that Bilbo had a magic ring but he let Bilbo keep the ring.

I wonder why they put that scene in.

If you watch LotR 1 after Bilbo uses the Ring, Gandalf instantly visits him and tells him that he should leave the ring because magic rings are always dangerous. This does not fit to Hobbit 3 because the Gandalf we know from movie 1 would never let Bilbo keep that ring.

In my eyes that makes not much sense. They should have just let the scene out of Hobbit where he says he knew about a magic ring.

What do you guys think about that.