Actually there is no morality in Nature. That is a human construct.You saying some undeveloped microorganisms should not be wiped away by a more advanced species happens to be contradictory to Nature's brand of morality.
Just as wanting to think perhaps that mankind is more advanced than other forms of life.
Depending on how you choose to measure, it just may be that a microorganism living naturally on a planet like Mars is more advanced than our DNA which apparently condemns us to hope only at best to be a visitor and even then to eventually long for the day that we can once again return to earth and go swimming and play softball and eat hot dogs on a warm sunny 4th of July.
You might want to appreciate what there is here before deciding to expend effort to muck it up on other worlds that we are ill suited to live on in the first place.