You don't need to explain your self just to make other people believe in you they have their own mind and decision in life , let them what they want to do . No one will understand you If in the first place they don't want to listened . Let them see it to happen so they can decide on thier own ,no need for more explanation you are just wasting your time and energy to the person that you know will not listen to you.
That's right! You can't force someone to believe what other people are saying. We have our own life, own problems to deal everyday. It is up to the person how he will live his life. So just mind your own business and maybe, the OP will not stress himself with what is happening around him. Let the people take care of their own business.