It seems that anarchists argue mostly with mini-archists, vegans argue mostly with vegetarians, young earth creationists argue mostly with old earth creationists, m theorists argue mostly with string theorists, etc, etc. Any theories as to why such a concentration of argument?
It’s easier to argue if one’s premises are similar. Arguing with someone holding an entirely different set of premises is likely to end in a shouting match.
There is the assumption it should be easier to convert them to your position?
Yes, Thomas Kuhn’s “scientific paradigm”.
On forums, maybe, but most people I argue with are obamanites 
people pay 99 cents a song now, when they could get it for free…
people would pay 10 cents for a song…to the original artist…
and people would pay a software creator and a movie producer…
the only thing that would change, would be the price for these things would have to come way down…
in other words…IP laws have unnaturally made the value of these items way too high.