The best thing to do is to not answer. Throughout history there is a pattern that when a technologically advanced civilization meets a less advanced one, the less advanced one eventually is subjugated or destroyed. Example: European civilization vs. civilizations in the Americas. The Native Americans, Mayans, etc, had a basic level of civilization in relation to weapons. The Europeans had guns and the American colonists had guns and also used biological warfare by, for example, giving Native Americans blankets infected with smallpox.
In World War II the Japanese military did very well until the Allies military produced advanced fighter planes and a military strategy that effectively drove the Japanese army off of one island after another, pushing them towards Japan. Then the U.S. developed the atomic bomb and that was it for Japan. (They did argue amongst themselves about whether to surrender or not, though, not knowing that the U.S. had one more atomic bomb ready to go and were considering using Tokyo as a target.)
All this is a moot point, of course, if the UFOs actually are from an advanced race of beings from this reality or an alternate /parallel reality. Any announcement that would be official that would say 'the aliens are real, they are here and we can't do anything about it' would cause massive panic. religious upheaval and a whole host of other societal problems that would make what is going on today look like child's play.
I think we should keep SETI going but if a signal is received and acknowledged as a repeatable signal we should not answer. I think the record on the Voyage spacecraft should never have been put on the craft. It's the old 'keep your heads down, you never know who might be shooting at you' approach but I think it's the most practical one at the moment.