That is nonsense. It might look like that, because the industrial players are able to cover both gankers and carebear needs and the prices at Jita are basically staying intact no matter what (at least long term - I already bought off some commodities and their price skyrocketed, but in matter of days it stabilized again), but that is because the industrial players are just able to produce so much. If no destruction occurs in highsec, then they have no reason to produce all these ships and modules that are destroyed on both sides. They will lose their job. Prices will probably stay intact even without destruction, but only because nobody will go under production cost and if there is no demand, the production will simply stop, probably with those players leaving completely.
But if we look at items that are looted or acquired by LP, if these blinged ships in highec never dies, they have no reason to buy these modules. Which will drive prices of these modules so low that suddenly escalations are pointless, lvl 4 missions are only for fun, and fw is not making any profit either. The only thing that will keep doing profit will be abyssal probably because of its gambling nature and production of junk. So eventually highec gameplay would basically shrank into hunt for perfect abyssal rolls. Which is basically how every other MMO(RPG) works. And which is why I don’t play them and I play EVE which is different and offers the thrill of being killed anywhere.
The destruction in highsec is higher than destruction in nullsec. Sure, some of the destruction is due to wardecs, but these wars are often targeted against nullsec and if we use definition of ganking to be any non-consentual pvp then I think we can include wardecs into this as well. So lets say the destruction in highsec is 50% of the destruction in nullsec.
If you say that this destruction has no impact on nullsec alliances, then that means that the destruction that happens in their regions have also 0 impact on them. Hence no destruction anywhere impacts nullsec alliances. And you might be even right, but does it matter then? Is it worth argumenting with?