I think I resent certain people with mental illnesses.
I hope you're joking. Who with mental illnesses are you resenting?
I'm resenting a man with a mental illness.
You need to be more understanding of people with mental issues. You shouldn't be resentful towards them just because of their health.
I know. I need to help the poor men with mental issues.
I understand that dealing with people with mental issues can be difficult at times, but they have limited control over their condition. Remember, "There but for the grace of God go I." Offer help, not resentment.