This is intended as a hypothetical situation in which you insert yourself and provide what you think is a wise course of action in terms of trying to share (or not share) Christ.
Here is the situation - you walk into a post office where you are on good casual terms with the guy (we’ll call him Bill) who works there just as another person is walking out. You can tell Bill is a little defensive for some reason. Then, as he scans your packages, he laughs out loud and says he wants to share a funny story with you - so you go along.
Bill says he shared with the person who just left that he had attended a drag event (men dress as women) and they tried to tell him about redemption. He is in absolute unbelief that someone would be so ridiculous. He says he leaves people alone as long as they are not hurting anyone.
Bill is expecting you to laugh along and clearly is not a believer.
So - what do you do?
Consider these things - if Bill talked about God and this other person behind their backs, will he not do so again if you try to share? Is this the right time to share if Bill is already upset by the other person perhaps being too forward?
I understand the Holy Spirit guides us, so please avoid simply saying to listen to the Spirit - not because I do not think that is a valid answer - but I think that shortcuts actually thinking through and learning wisdom.