There is nothing wrong with a fork. Let's just make sure the exchanges allow the exchange of both. If there are exchanges that intentionally block one over the other, the exchange is not a supporter of free markets.
The only problem is that CURRENTLY, real world merchants like Dish, Expedia, etc will only accept "Bitcoin". They will not bother accepting two coins, so most likely the fork with less mining power will die quickly and there will be miniscule demand for it.
In the future if crypto becomes more mainstream, a fork that leaves two currencies will be more viable.
I would not be so quick to assume that real world merchants will accept "only Bitcoin." First of all, some of these merchants were doing perfectly fine before accepting Bitcoin. They got into Bitcoin for a reason.
Secondly, it is entirely possible to build a "merchant service" whereby a Seller can accept any currency that the Buyer chooses, and have it instantly converted to their own currency. All this requires is more people to adopt Bitcoin and/or any other currency out there and to grow the exchange markets. Exchanges are very critical in this entire ecosystem.