"Pure hogwash!"
I suggest you look up the word Monopoly, before spraying pig water about:)

"Monopolies are the natural outcome of a truly free market. If someone chas a better product or delivery method, they outcompete the opposition. This is like natural selection of species."

May I remind you that an absolute or truely free market has never been seen on the face of this planet. We might get one which is closer with globlism- maybe.

"The problem with "free markets" is that the successful monopoly then starts diversifying into other ecological niches, using its established infrastructur to legally get a margin on its competitors in other unrelated markets, or illegally cross subsidising."

This is simply an example of a relatively free market becoming less free.

"How many companies write operating systems for home PC's, and sell them in bulk?"

I'm not saying their are no advantages to monopolies such as Microsoft.
And I do generally like the idea of the State making and controlling money- at least at this point in time.

"Luckily for progress, monopolies usually lose inertia and become moribund dinosaurs while small hot-blooded innovators scurry around their feet and pick up the crumbs that become the great businesses of the future, but if successful, they, too, will have a monopoly in their own niche..."

I think the word you are looking for is market dominance- which is not the same as a monopoly.

"Only legislation and intervention stops there being far more obvious monopolies."

That's true the monopolies are generally hidden in plain sight by govt legisations. The big three America Auto makers are good example of this- 3 companies can't be a monopoly, right? Mono means 1, and 3 isn't 1, so it can't be a monopoly, simple.