Because of the risk that is in bitcoin it won't stop me from telling people about bitcoin which will better their life if they found it interesting.
If you see during the conversation they are trying to counter question you trying to prove that you are wrong and Bitcoin isn't a good thing or something, that is when you should smile and end the conversation instead of wasting your energy on people that are ignorant and let them regret it in the future.
It depends, I mean, if they listen attentively to your explanation of bitcoin and then they make an argument from their bitcoin knowledge against you. It means they are interested in bitcoin but still have some doubts and it is your duty to answer their doubts, not to end the story abruptly. But if they are stubborn and ignore your explanations, it's time to end the bitcoin story to avoid wasting both of your time.
Bitcoin is still unfamiliar to many people, so once we accept that we want to spread bitcoin to everyone, we should prepare ourselves for rejection or criticism.