In that scenario you're saying that the Martian landscape itself is not worthy of preservation, while any microorganisms could be. Both amoeba and rocks have no claim to consciousness etc., so why is one worthy of preservation while the other is not?
OP is not interested in preservation for preservation's sake.
It's not like we should care about the consciousness of microbes. What he meant, as I read it, is that if there are microbes we'll want to sample them and study them BEFORE we change the landscape and possible kill them.
