Paul speaks of anything that would prevent a person from trusting in Christ as if it were a physical object over which that person trips and falls. Alternate translation: "We do not want to do anything that will prevent people from believing our message" (See: [[rc://en/ta/man/jit/figs-metaphor]])
The word "discredited" refers to people speaking badly about Paul's ministry, and working against the message he proclaims. This can be stated in active form. Alternate translation: "we do not want anyone to be able to speak badly about our ministry" (See: [[rc://en/ta/man/jit/figs-activepassive]])