In my not so humble opinion I think that's a really naive and ignorant way of looking at it. What if there is life on Mars that's unique to that planet? Introducing our microbes and germs to that planet could potentially wipe out the native fauna.
It's extremely unlikely that germs that evolved under Earth conditions could out-compete the germs that evolved in Mars conditions in the Mars environment.
There are certainly such a thing as an invasive species, but that's survivor-bias. If you move some alligators to the desert they are not going to decimate the local camel population.
