The discovery of ETs would not undermine the case for the design of terrestrial life one bit. The situation for Darwinists is very different.
Scientists in Western cultures have been trained to see the world through a materialist metanarrative where the only acting players are matter and energy.
Let’s turn the SETI telescope around. Would extraterrestrials be justified in inferring ID from patterns on the earth?
We have Trojan asteroids in our Solar System that orbit with Jupiter. But, there isn’t any evidence of actual Trojan planets.
Scientific materialists must live in a state of cognitive dissonance.