This discussion seems to be flowing through 2 pathways.
1) Is there other intelligent life in the universe.
2) Is Earth being visited by "space craft" built by other beings.
I think 1) is a good possibility.
I think 2) is unlikely. There are many obvious reasonings that point to the improbability of others beings travelling here. These out way the fewer reasonings that may support the possibility of space craft visiting Earth.
Personally, I think all UFO sightings are mistaken conclusions, wishful/hopeful thinking, deceitful reporting, fame/attention seeking, etc.
This is certainly an interesting and enjoyable discussion.
