"Dumping" (selling at an artificially low price) is widely considered an attack on economic activity of the competitors, even though it may spur the economic activity of the consumers of the products being dumped.

In this regard, the Chinese government pouring large subsidies into solar panel production both spurred the economic activity around installing solar panels, and attacked / thwarted in around production of the panels themselves, if the production happens outside China. Only the US was able to somehow develop solar panel production.

"attack on economic activity of the competitors"

Thats competition. It is a feature of markets.

not a bug.

Not when its done with the help of a government.

why not?

I'm not really disagreeing with you as it's not like there is a 100% true definition of a free market, different people can have different conceptions, but the original Adam Smith / classical view is that a free market should essentially be 100% driven by the private market on supply and demand - with as little government intervention as possible on either side of the ledger (subsidy or blocking)

Monopoly is a free market game and thete is only one winner. Free markets as such is an utopia dream.

Except it isn't at all. The properties to buy all have a fixed price, costs of houses/hotels are fixed, rents are fixed and can't be adjusted, and most importantly, a) you can only buy a property if you randomly happen to land on it and b) people have no choice of what property to stay at (again, chosen by random dice)

mmm by that definition, which market is truly free market again? I'm not sure you can find one tbh

Commodities, large number of buyers and a large number of sellers all buying/selling an equivalent product.

No buyer has power to set prices and no seller does either.