> One side thinks that it's vital to allocate resources fairly
It is actually capitalism that thinks that it is vital to allocate resources fairly. Communists, on the other hand, think that resources should be allocated _equally_ with no regard to fairness. "To each according to his need."
> this can be done efficiently if only people would be good enough.
And until people get good enough, which in reality will never happen, communists think that the use of force to take from those who have and give to those who dont is perfectly justifiable.
> The other side thinks that market forces are the only way
Nope. The other side thinks that central planing and big goverment are a source of abuse of power. A free market isnt a perfect solution, but it is the lesser of two evils. If nobody has massive power, nobody can abuse power massively. There inevitably will be some abuse in a free market, but not in the orders of magnitude of, say, North Korea, Soviet Union, Nazi Germany and other central planning epic fails.
> deviating too far from this in the name of fairness
It is not done in the name of fairness, but in the name of equality. If fiarness was the goal, communism would be the side trying to not interfere and to leave everybody alone. But it is not. Communism is the side advocating maximum interventionism, of requiring (and enforcing) sacrifices for a centrally planed "greater good" etc.
> Extremists on both sides make it hard to have a sensible conversation.
In my view, the only way to solve it would be to create communist and capitalist zones, and make it legally impossible to change that economic basis of a zone. The "conversation" would then amount to fans of capitalism and communism moving to their preferred zone. Neither side would be trying to forcibly make the other side live under their economic religion.
The problem is that the left doesnt actually want to draw that border between takers and makers, because they _are_ takers trying to get total control of the makers in order to exploit their productivity.
As long as communists are able to get control of a whole state and then forcibly redistribute _other_ people's wealth, there will be a state of perpetual low-intensity warfare between the left and the right. Knowing that once you give communists a single finger, they will feel entitled to the whole hand and try to forcibly amputate it, is not in any way extremism, but knowlege of history paired with a sense of self-preservation.
What point does it make to have a conversation with people who are basically trying to legally mug you?