It wasn't the scenario suggested because besides it being infentestimentally likely its still possible that our planet has infected another with life.
What I get testy about is when folks abuse logic and orderly thought. In this case its using Occam's razor in the exact opposite way to rule out the most likely explanation and to rule in one that has no evidence that it occurred and if it did it had occurred, it would require a string of several virtually impossible events perfectly following one after the other.
You stood Occam's razor on its head.
It only seems impossible to you because you do not understand the nature of -- or number of -- fungal spores on this planet.
I've had similar discussions with people who don't understand the nature of radio wave propagation. They cannot accept the notion of a little shirt-pocket sized radio putting out half of a watt, filling over 100,000 cubic miles with a usable signal -- yet, it can, and does happen. One injured climber used his FRS radio, output of maybe 350 milliwatts, to call for help from the side of a mountain. A kid in his backyard heard him -- from about 75 miles away. In another case, two guys talked to each other with similar radios from two mountaintops, about 110 miles apart. How can such a tiny amount of power reach out so far?
The thing is, its ability to traverse that distance is not contingent on your ability to comprehend how it could happen.
So, how do you explain the Mars rocks found on Earth? Or do you dismiss them too, because you don't accept that they could happen?
It's important (IMO, at least) not to stand logic on its head by declaring what can and cannot exist on the basis of preconceived assumptions.
I've shot rabbits using very small shot, that patterned quite wide. I guess "the odds of any one of those pellets hitting the rabbit was laughably, impossibly small", but, the rabbit wasn't laughing.
I have no doubt that an expanding cloud of dirt, dust, and spores, could travel the distance to mars -- just as its rocks (and doubtless other stuff too, like dirt and dust) reached here. And, I have no doubt that once reaching Mars' orbital position, it would create a wide enough pattern to pepper the planet nicely.
And, I've no doubt that once there, they'd likely have found a variety of "landing zones" conducive to growth.
You seem to be disimssing everything I say, as if you know so much more than I, about... everything. And, that assumption proves (to you) that whatever I say on the subject is therefore unworthy of anything but dismissal. I don't see you either comprehending, or even stopping to consider what I've been trying to explain to you. Instead, I'm met with arrogance, and a measure of demeaning hostility. Strange, very strange.
When pressed for a reason for the hostility, you provide an answer that basically boils down to me being a dummy.
In other words, I'm weighing whether or not I should dismiss you as someone who's got issues that he doesn't feel like resolving, other than by taking a free shot or ten at me. And frankly I must say it's not looking too good for you at the moment (in terms of my willingness to further engage you in this discussion).