People tend to ask “Do aliens exist?”, but a more interesting thought is “What if aliens do not exist?”.
If there are no aliens in this vast universe, then that indicates that we are the only form of intelligent of life. If so, are we not one of nature’s greatest creations and wouldn’t the destruction of such an achievement be foolish? Because if humanity was to become extinct, then that would result in the only species able to think of such a question ceasing to exist.
This theory can further be understood as saying that Earth is the only place in the universe where life can and does exist. Ergo, we (as possibly the last intelligent life) should protect the planet from destruction so that life can continue in the universe.
However, if aliens were to exist, it would be better to ignore them and not search for them. Many dream that they will be benevolent, bringing us advanced technology and knowledge, but in the history of mankind, there is rarely a situation where two worlds meet and the weaker is not looted, enslaved and destroyed.