that's not but what is:
is failing to understanding that a feature that is more valuable will have an impact.
what if that value is laundering stolen coins? the arb opportunity will be 0ver 10% and there are about 1,000,000 stolen BTC out there.
what if some nation state: whats to use blockchain technology, and invests a failing fiat system or there gold reserves in a SC that is inflationary but comes with demurrage if saving in a private wallet and interest when held with a CB or some other feature that appeals to the 99% that is not Bitcoin. it is a great opportunity for Bitcoiners to arb initially until the arb gap is closed. the goale here is to make Bitcoin attractive to Nation-State's note there isn't a Nation-State that should feel safe with bitcoin growing as it is.
What if ? Well 1,000,000 in, laundry time, 1,000,000 laundered coin out to the main chain.
Are you serious when asking these questions? Do you seriously believe that there are an incentive for someone to leave their coins on a potentially less secure Sidechain when it's only feature is to launder coin and that somehow this feature is more valuable than the whole Bitcoin mainchain?
Here you go again with your GOVcoin argument

You know what's the problem with this paranoiac idea, other than paranoia itself, is that GOVcoin is... guess what? An altcoin! And altcoin, well... they already exist.
Sidechains did not create altcoinsSidechains do not enable altcoins