This is a community and we collectively decide what is fair and right. You are neither.
What is "fair" is not necessarily what was agreed upon. Some may argue that the interest rates that Loan Shark is charging (and what his borrowers are agreeing to) is unnecessarily high, however his borrowers should still pay this interest rate because it is what they agreed to.
The interest rates that most borrowers charge around here would probably be considered "predatory" in much of the Western world.
I am not so sure that it is appropriate to ask for both BCH and BTC for outstanding loans. I don't see anything in his loan agreements that would compel his borrowers to repay both BCH and BTC. One party to a contract does not have the right to unilaterally change the terms of the contract without the other party of said contract accepting the modified terms.
I would also point out that BCH is trading at roughly 0.179 BTC and BTC is trading at >100% from where it was trading only days ago, and is roughly at the ATH.
I would say that interest paid by borrowers is what compensates Lone Shark for the loss of being able to use BTC for whatever he wants, including to use it to receive BCH, when possible. if Lone Shark was not lending out his BTC, he would have the opportunity to lend it out on bitfinex (or another exchange), or invest it in an ICO, or invest it elsewhere, and it would not be reasonable to have borrowers repay hypothetical returns on these investments plus interest for the loan.
Again perfectly worded. Someone that sees the bigger picture from a fair perspective.
Thanks.