it's an overreach of state power to tell private lenders what rate of interest they can charge. these are private contracts and people enter into them freely of their own will. restricting interest rates is islamic fundamentalism, and it reeks of anti-semitism. it should be rigorously opposed by everybody interested in freedom.
the actual result of a policy such as this is that emergency loan services will go out of business, taking away a service that people sometimes rely on and need. these loans will continue to happen, but they'll happen under the table, with more severe outcomes for people that can't pay the debts. lending out money to high-risk people at 10% interest will no longer make business sense, and the businesses will stop doing it. the result is not a decrease in interest rates, but a decrease in access to lending.
you want to continue to legalize and regulate high interest lending so it can be overseen by law enforcement, not drive it underground and make it worse by trying to ban it.
the state might step in and provide high risk loans at low interest if it wants, but it wouldn't have to interfere in private decisions made by consenting adults in order to do it.