I don't get it. It will actually be bad for BOTH chains if indeed Bitcoin forks into two. Some people who are following the space could see this as a weakness and another reason not to start investing or accepting BTC as payments. Imagine if you were a merchant and you have to go thru and be involved in this sh*t, with all the debates and the drama. And worst of all the uncertainty of BTC's future.
It presumes that development will continue on both chains and that adoption of both chains will grow to surpass the current usage of the single chain we use now. The idea is that Bitcoin is still in an early usage state and not mainstream so if this type of fork happens it is possible that both chains can still grow and appreciate from new users entering into the ecosystem. The ideal though is to remain a single chain because two chains impacts the value of all other coins relative to Bitcoin and Bitcoin B and brings forth a lot of short term drama that is not enjoyable. Merchants will need to choose a side unless the payment processor accepts both, Bitcoin machines will need to choose a chain unless they accept both and maybe add a few alt-coins etc.