We have been told that listening to church sermons about fire and brimstone is a risk factor for spirit attachments. Does this apply also to watching horror movies or frightening scenes in motion pictures?

This applies to them as well. Any moment of fright will lower the vibration, open the defenses, and provide an energetic match to the energy the spirit meddlers are seeking. This will serve as a beacon to them as well, as they will sense when the energy is being created and it will radiate out from the human and that consciousness will be perceived and will serve as an attractant much like a moth to a flame and the spirit meddlers will come calling, and if they can penetrate will do so.