It might work. You never know what you may encounter on entering a new biosphere. When the white men came to North America they passed diseases on the the Indians that wiped out whole tribes. They also picked up syphilis from Natives in the Caribbean (who were not affected by it, but were carriers) and it devastated the Spanish nobility and spread rapidly across Europe.

So why not have a scenario where Earth germs prove fatal to Martian visitors?

The thing is, it allowed H.G. Wells to make a powerful point about man's pride being humbled in the face of Nature...and a spiritual point as well, concerning Divine Providence. In his time, there were very few atheists. In Crazy Horse's culture, there were none. It is the untrammelled pride of the complex human mind that suggests there is no God, because the mind wants to be God itself. The human mind is Oedipus attempting to slay his divine father and supplant him. That is the essential problem in a nutshell. Wells' tale is a cautionary one, a warning to the overly proud human mind that has the nerve to appoint itself as judge, jury, and executioner over an existence which it then has the nerve to deem...meaningless.

There are two results to such a credo...pride...and despair...because what use is life at all if life in the end should prove meaningless?