The more convinced we are that we just can't find the fascinating extraterrestrial life, and the more sure we are that our dirty, smelly, boring Earth bacteria will contaminate and destroy it, the less we will be able to explore in general. We already know we're not keeping even new, unknown species of bacteria out of NASA's clean rooms. What makes anyone think we haven't already contaminated Mars and the Moon? I say we give up on finding extraterrestrial bacteria for now, and instead try to spread Earth bacteria to places like Mars and the Moon.
And maybe discovering some form of Earth bacteria that can survive or thrive on other planets would be a really useful discovery. Maybe that would be the first step to terraforming those places.
Mokalus of Borg
PS - Or maybe we doom a bunch of bacteria to a slow, cold death.
PPS - Which is, frankly, better than doing so to people.